The Central Intelligence Agency's secret aid to the insurgents fighting the Soviet invaders in Afghanistan has mushroomed into the largest U.S. covert operation since the Vietnam war era, according to informed sources.

With Rep. Charles Wilson (D-Tex.) as a chief catalyst for the rapid escalation, Congress has nearly tripled the Reagan administration's initial request for the Afghan program to what will amount to about $250 million for this fiscal year. This would amount to more than 80 percent of the CIA's annual expenditures for covert operations, the sources said. In addition, three other countries in the Middle East and Asia are expected to provide $200 million. With this money, the annual aid package to the Afghan insurgents is approaching $500 million. The sources also said that there is discussion that the insurgents could use $600 million in the next fiscal year.

The Afghan operation and the manner in which it has expanded are becoming subjects of heated controversy in the administration, the CIA and Congress.

A number of these officials, who do not want to be identified, said that the program has grown too much and too fast. These sources said it is in danger of getting out of hand and may trigger an escalation of Soviet military operations in Afghanistan.

Others, including Wilson and congressional supporters, said that the U.S. government is not doing enough, that equipment being used is second-rate and that the insurgents are not getting enough supplies and ammunition. Some have advocated supplying new, sophisticated U.S.-made ground-to-air missiles, but the CIA vetoed this, according to the sources.

Of particular controversy has been Wilson's successful effort to obtain money for the CIA to supply advanced, heavy antiaircraft cannon to the insurgents, a decision a number of officials view as a potential escalation.

By year's end, the U.S. program, which supplies weapons, ammunition, clothing, medical supplies and money for food, is expected to support an estimated 200,000 to 300,000 full- or part-time insurgents who are battling a Soviet army of 110,000 troops in what intelligence reports and various eyewitness accounts describe as one of the most brutal, savage conflicts of modern times.

"This is a program that is on the verge of blowing up," one intelligence official said. "It is an area of the world where there are great tensions . . . . The blinking red lights are going off in that region now, and the focus is shifting from Central America."

One congressional critic of the escalation said, "We should have learned from Vietnam about over-technologizing primitive people." Another intelligence official said, "We're going to kill the program with success."

Though there are hundreds of cases documenting human rights violations by the invading Soviet army, the U.S. government now has confirmed reports that the CIA-supported insurgents drugged, tortured and forced from 50 to 200 Soviet prisoners to live like animals in cages.

In addition, congressional sources said that the insurgents may be assassinating Soviet military officers and administrators. U.S. intelligence officials said they cannot and do not control the operations of the resistance fighters and have no knowledge of any assassinations.

The large increases began in the fall of 1983 with a secret Wilson amendment to the defense appropriations bill rechanneling $40 million of Defense Department money to the CIA for the Afghan operation, the sources said. Money Destined for Cannon

Part of this money was for the new, foreign-made, heavy antiaircraft cannon. Another $50 million for more supplies and weapons was reprogrammed at Wilson's initiative in the same way last July. The Senate, at the urging of Malcolm Wallop (R-Wyo.), chairman of the Senate intelligence committee's budget subcommittee, then took the lead in increasing the annual aid to the point where it is about $250 million for fiscal year 1985.

The specific amount for 1985 is difficult to calculate, according to sources, because there is some unspent money from previous years that is expected to be used this year. But the sources said spending will range from $250 million to $280 million.

It is clear from interviews with more than 20 officials familiar with the Afghan covert aid program that over the last 18 months, while public attention has been focused on the CIA's activities in Nicaragua, Congress opened the dollar flow to this much-less-visible program.

By contrast, Congress last year cut off funding for opponents of the government in Nicaragua that was one-tenth the size, costing $24 million a year and supporting 15,000 "contras" fighting the Sandinista regime.

Some in the Reagan administration and the CIA at firsv opposed the large increases in the Afghan operation and were not sure that the supply line, which runs secretly through neighboring Pakistan, could absorb the increased flow. But officials said that after facing years of public congressional hostility to the secret war in Nicaragua, the CIA finally went along and welcomed support in covert operations aimed at thwarting the Soviets in Afghanistan.

"It was a windfall to them," said one congressional intelligence official. "They'd faced so much opposition to covert action in Central America and here comes the Congress helping and throwing money at them, putting money their way and they decided to say, 'Who are we to say no?' "

Increasing the Afghan program also gave Congress a chance to show it is not soft on communism and Soviet expansionism, congressional sources said. "Over the last two years," one senior administration official said, "as the Nicaraguan operation became the bad war, the one in Afghanistan became the good war."

The decision to supply the new antiaircraft cannon, for use against Soviet helicopter gunships that are deployed against civilians and insurgents, has been especially controversial. One intelligence official said, "When this weapon gets in and if helicopters start getting shot out of the sky with regularity, we've got a problem . . . . A weapon like this could force the Soviets to become more indiscriminate in their use of force. They could begin much more bombing. It could change the equation radically."

Some intelligence officials cite Wilson's involvement with the new antiaircraft cannon as an example of what the CIA calls "micromanaging" of their operations from Capitol Hill.

Wilson confirms his role on behalf of the Afghan resistance but declines to discuss the numbers relating to his legislative efforts. Wilson said in an interview that the new cannon, with armor-piercing explosive shells, "means there aren't going to be any more Soviet helicopters going back to Kabul the Afghan capital with holes in them. They're going down."

Of the covert aid package increase, Wilson said, "We're talking about peanuts. We're talking about one B1 bomber. I'd give them five." (The B1B bomber costs about $200 million.)

Wilson continued, "There were 58,000 dead in Vietnam and we owe the Russians one and you can quote me on that . . . . I have had a slight obsession with it, because of Vietnam. I thought the Soviets ought to get a dose of it . . . . I've been of the opinion that this money was better spent to hurt our adversaries than other money in the Defense Department budget."

House colleagues and members of the Senate tell of Wilson's dogged effort to secure support for the Afghans and the new antiaircraft cannon. Sources said that Wilson even arranged a mule-breeding program for the resistance to haul the new cannon, ammunition and other supplies into the mountains of Afghanistan.

The sudden mushrooming of aid, through supply pipelines set up after the Soviet invasion in December 1979, also has created massive control problems. By some accounts, as little as 20 percent of the weapons and supplies reach the Afghan resistance because the material must travel through a long, complicated supply route. The CIA maintains that 80 percent is getting into the hands of the fighters.

Government and intelligence reports also show some cases of human-rights violations by the insurgents. One well-informed source said recently, "There are 70 Russian prisoners living lives of indescribable horror." Several administration officials said that the United States is going to have to face this problem.

According to two sources, the insurgents have made requests for assassination equipment and asked for information on locations of high-ranking Soviet generals and administrators. But there are no proven, clear cases of assassination. The CIA is prohibited by executive order from supporting assassination directly or indirectly.

One source said that the resistance is "not going to worry about a presidential executive order and they are certainly going to ask for sniper weapons and if they ask for them, they're going to get them."

CIA officials said that they have no way of preventing individual tribesmen or resistance leaders half a world away from taking such actions. "We don't control the operation," one official said. "We support it."

A December 1984 report from the Helsinki Watch Committee, an independent human-rights group, entitled "Tears, Blood and Cries, Human Rights in Afghanistan Since the Invasion, 1979 to 1984," describes terror tactics including torture and assassination that allegedly are being used by both sides. The 212-page report devotes 172 pages to the Soviets and 16 pages to the resistance; the group apparently found substantial violations by the Soviets.

Through all of this, officials said the government of Pakistani President Mohammed Zia ul-Haq is walking a diplomatic tightrope because most of the covert aid is channeled through his country. Two key intelligence sources said that the massive increase in the covert program gives Zia leverage to demand more U.S. aid for his country. These sources voiced fears that, in the extreme, Zia's position might be so strengthened that he would request assistance in building his nuclear weapons, a goal at odds with U.S. policy and denied by Pakistan.

Many details of the Afghan covert aid program have been reported since the operation began during the Carter administration. But officials said the sudden increase in the last 18 months and the lobbying of Wilson with the support of most members of Congress jave allowed little time for the administration or the Hill to debate the consequences of various tactical decisions, such as the new antiaircraft cannon, or the funding increases.

Wilson's efforts began in earnest after he and then-Rep. Clarence D. Long (D-Md.), longtime chairman of the appropriations subcommittee overseeing foreign aid who was defeated last November, returned from a trip to the Afghan resistance camps in Pakistan in August 1983. CIA aid to the insurgents was about $30 million that year, and the agency had not requested an increase for the next fiscal year, according to sources.

In a recent interview, Long said the insurgents told him during the 1983 trip that "they wanted something to knock down helicopters." He said that Zia agreed the insurgents should have improved antiaircraft weapons.

At the time, the insurgents had only machine guns, which often hit and damaged the Soviet helicopters but did not have the firepower to bring them down. In addition, the Soviet-made SA7, a shoulder-launched, heat-seeking missile, one of the items purchased as part of the covert program, has turned out to be unreliable.

Long said that Zia suggested a new cannon and gave its name. "If it was American-made the Soviets would trace it to Pakistan and he Zia didn't want that. He suggested we get foreign-made guns . . . . He was perfectly willing to take a chance if it couldn't be traced back to him," Long said.

As the next step, Long said he asked Wilson to offer the Afghan aid increase amendment because Wilson was a member of the defense appropriations subcommittee and a member of the House-Senate conference committee that worked on the defense appropriations bill.

Wilson confirmed this, saying, "I was the instrument of Long's idea." Wilson said he came up with the amount for the initial amendment, and said he did this by pulling a number "right out of the sky." Other sources said it was $40 million.

Wilson said he conferred with some officials at the CIA before, but they said that "they were shy about increasing their budget" more than had been approved by the House and Senate intelligence committees for other intelligence matters and operations. Budget increases usually come from the authorizing committees, which, in the case of the CIA, are the two intelligence committees. Because he is not a member of the House intelligence committee, Wilson said, "It was the only vehicle I had as a member of the House Appropriations Committee." Amendment Proceeded

He and Long went ahead with the amendment with the purpose, according to Wilson, "of trying to demonstrate that money didn't matter because it was such a worthy cause." The first $40 million increase was for clothing, boots, medical supplies and "rapid-fire cannons" for antiaircraft defense, sources said.

Wilson, who has made five trips to the region, said, "Every trip I made, the freedom fighters talked about bullets bouncing off HINDs Soviet helicopter gunships and how they needed armor-piercing explosive shells."

Wilson said it is unusual for a congressman to add money to a covert program and that he knows of no other such case.

"It was an easy sell," he said. Wilson reportedly had no trouble persuading the members of the House-Senate conference committee that the insurgents were fighting courageously and were not asking for food or medicine but some way to defend themselves against the gunships.

After the House-Senate conference approved the $40 million amendment, Office of Management and Budget Director David A. Stockman sent a letter late last February requesting the House and Senate intelligence committees to approve the reprogramming. A source said that the administration went along because of belief in the Afghan program and because it was a comparatively small amount requested by the House Appropriations Committee, which generally has supported administration requests for the Pentagon.

The deputy undersecretary of defense for policy, retired Army Gen. Richard G. Stilwell, reportedly objected to the loss of the $40 million from the Pentagon, and one source said that a Defense Department study described the new cannon as the wrong weapon for a guerrilla war.

In March 1984, the House intelligence committee approved a limited release of the money, while asking the CIA for a report showing that the advantages of the particular cannon outweighed its disadvantages.

On the Senate side, Barry Goldwater (R-Ariz.), then-chairman of the Senate intelligence committee, dug in his heels and refused to approve release of the money because he reportedly did not think it was the right weapon.

But Goldwater changed his mind in the first week of April 1984 after Deputy CIA Director John N. McMahon wrote the Senate and House committees to say that the CIA supported use of the weapon. One official said that the CIA was not familiar with the particular cannon and had to obtain one for testing.

Both committees then approved a limited test of nine of the cannons. They are due to arrive in several months on the battlefields in Afghanistan, the sources said, and more will be provided if the weapon proves itself.

The cost of each new cannon, plus transportation and initial supplies of ammunition, is put at about $1 million. Because the weapons are rapid-fire and the armor-piercing shells they use are expensive, some estimates suggest that millions of dollars will have to be spent to supply enough ammunition each year. Concern about this expense and the overall impact the new cannon may have in Afghanistan was expressed by a number of Republican and Democratic members of the Senate intelligence committee during a briefing on the matter last year, according to sources.

Several sources said that there is no effective countermeasure to the new cannon. On the other hand, the Soviets have been able to employ countermeasures against the SA7 heat-seeking missiles, and many of those missiles supplied to the insurgents have turned out to be duds.

For his part, Wilson said the cannon will not amount to an escalation in Afghanistan, and the Soviets should be made to pay a high price. "I think it would be immoral not to help . . . . I don't want the resistance fighters to give away their lives too cheaply."

A number of congressional supporters wanted initially to supply U.S.-made Redeye or Stinger ground-to-air, heat-seeking missiles, but the CIA blocked that because those missiles could be traced too easily to the United States.

Wilson cites reports showing a pattern of the brutality of Soviet operations in Afghanistan, including massive bombing raids that have driven millions of Afghan people across the border to neighboring countries, especially Pakistan. Wilson said that the Soviets have used booby-trapped toys to maim Afghan children as part of their terror campaign. Another official confirmed that there is such an intelligence report.

Congressional support for the Afghan covert aid program has been bipartisan and enthusiastic. Last fall both houses unanimously passed a resolution saying it should be U.S. policy "to support effectively the people of Afghanistan in their fight for freedom." But to protect Pakistan, the pipeline through which most aid flows, the program has been covert and handled by the CIA.

Though there has been general agreement that the Afghan operation is a "good war," there has been disagreement about its specific objective going back to when the Carter administration began covertly supplying the insurgents after the Soviet invasion.

A senior official in the Carter administration said there were serious questions from the beginning. "The question was, do we give them the insurgents weapons to kill themselves, because that is what we would be doing. There was no way they could beat the Soviets.

"The question here was whether it was morally acceptable that, in order to keep the Soviets off balance, which was the reason for the operation, it was permissible to use other lives for our geopolitical interests." General Agreement Remains

Now, five years later, there remains general agreement that the insurgents cannot win, although the CIA has reports that the resistance has done well in the last eight months. But supporters of the program such as Sen. Wallop are troubled by the lack of clear objectives.

"I don't know anyone who believes we will overthrow the Soviet-supported regime in Afghanistan," Wallop said, "so what does anyone define as success? You have got to have in mind what you want to do, and we don't in this case."

Others criticize CIA management of the operation. One well-informed official said that resupplies of guns and equipment get doled out to the resistance groups after successful operations, almost as rewards, rather than as part of a well-orchestrated campaign. "This whole thing is conceived as a supply operation, not a war operation," the official said.

An administration official involved in Afghan policy said, "Our policy is to get the Soviets out basically . . . . we have tied up about 1 percent of their Army . . . and the cost to the Soviets is about $4 billion a year and the total cost since 1979 is about $16 billion."

Other sources were skeptical about these numbers and note that the Soviets still would have the expense of maintaining that part of their army even if there were no Afghanistan war.

There is another theme that runs throughout interviews with officials, one that reflects the delicate nature of limited war. While denouncing Soviet actions and brutality, many officials noted, with varying degrees of emphasis, that the Soviets have imposed some limits on their actions.

"One of the important things is restraint," said one administration official, "and that includes restraint on our part . . . and restraint by the Soviet Union.

"You've got to consider what they haven't done to Pakistan and others . . . . Afghanistan is on their border, and you have to believe the Soviets could, if they chose, march in with sufficient troops to do the job."

One congressional official called that statement "ludicrous," adding, "This represents the kind of self-delusion according to which the Soviets and we have an unspoken, gentleman's agreement to never go for the jugular.

"Since the Soviets have disproven this constantly, this view can only be held through a heroic effort of self-deception," the official said.

Many of those interviewed expressed concern that the money and supplies get passed through so many hands -- "a board of Pakistani generals," in the words of one source -- that the hundreds of millions of dollars are not accomplishing that much.

Alexander Alexiev, a Rand Corp. analyst who has visited the region for the Defense Department, said, "Corruption is rampant . . . . Some of the political leaders live in fancy villas and have fat bank accounts, while the fighters don't have boots five years into the war."

He said he talked to one resistance leader who had only a hand-drawn map of the province that was his home base.

One senior member of the Senate intelligence committee, who said he will continue to support the program, said, "It's like tossing money over the garden wall."