Congressional supporters of the resistance movement to the Soviet occupation of Afghanistan, backed by outside lobbying groups, are pressuring the Reagan administration to improve the effectiveness of its military aid to the guerrillas and end its ban on the delivery of American-made arms, particularly antiaircraft weapons.

These congressmen also are seeking to get the administration to name a high-level White House presidential adviser to coordinate U.S. policy toward Afghanistan and the expanding American aid to the rebels. The Central Intelligence Agency, the Agency for International Development and the Pentagon each has its own program.

One of the chief charges being leveled against the administration by U.S. supporters of the Afghan guerrilla struggle is that Washington's policy has no clear objectives. The critics are charging the White House has never made up its mind whether it wants a clear-cut Afghan guerrilla victory or a low-level campaign of harassment of the Soviet Union.

Outside analysts and even some administration officials concede that six years after the start of the U.S. aid, American objectives remain ambiguous -- caused by Washington's concern over the Soviet reaction to a more direct U.S. involvement and by caution in Pakistan toward the conflict.

Despite this ambiguity, the U.S. commitment to the guerrilla forces has grown steadily. While the level of funding for the CIA's Afghan operation remains a secret, congressional and other sources say the House and Senate intelligence committees initially approved $470 million for covert military assistance last spring for the current fiscal year.

Later, there were reports that Congress had approved a supplemental $300 million in aid over two years. It is not clear whether the supplement is reflected in the $470 million figure or is in addition to it.

Congress now has approved $15 million in annual humanitarian assistance, which AID will administer, and another $10 million for the Defense Department to cover the cost of transporting such nonlethal items as clothes and blankets to Pakistan for Afghan refugees.

While President Reagan repeatedly has stressed his commitment to the Afghan resistance, the main thrust for steady increases in aid has come from Congress. According to a former Senate Select Intelligence Committee staff member, the committee each year has doubled the administration's initial request.

Unlike divisive debates over the administration's desire to provide covert military aid to rebel groups fighting the Sandinista government in Nicaragua or Marxist rule in Angola, Congress has achieved consensus on providing more assistance to the Afghan rebels.

This has made the administration nervous about the implications for its relations with Moscow.

Administration spokesmen defend the current program as a major success, citing the ability of Afghan guerrillas to fight the estimated 118,000 Soviet troops stationed in Afghanistan to a stalemate and claiming that they have shot down nearly 800 aircraft -- a figure met with some skepticism by independent observers.

The spokesmen say the United States is doing all it can, given its dependence on Pakistan to funnel aid to the rebels, and that the administration's general caution only reflects Pakistan's.

"We have a right to be cautious. We're dealing with another sovereign country and it could blow up in our face," said one U.S. official.

The administration's critics also charge a lack of direct U.S. control over the delivery of U.S.-purchased arms, which, U.S. critics and guerrilla leaders alike charge, has resulted in many weapons not getting through to the battlefield.

Some congressmen also are complaining that the CIA, in the absence of a clearly stated White House objective in Afghanistan, is making policy on its own. "It's so damn obscure what the policy is. There is no clear objective," said Sen. Malcolm Wallop (R-Wyo.), adding that CIA Deputy Director John McMahon "has told me it U.S. aid cannot be too successful."

Wallop and Sen. Gordon J. Humphrey (R-N.H.) have been instrumental in lobbying the administration for a clearer, all-out commitment to an Afghan guerrilla victory.

Other congressional sources said McMahon had argued before the House and Senate intelligence committees last year against provision of American antiaircraft weapons or a much larger covert program, saying the administration was concerned they might provoke the Soviets into retaliating against Pakistan and believed authorities there would not agree to either.

Rep. Charles Wilson (D-Tex.) asserted that the CIA and McMahon are taking "a bum rap" and that the agency is doing "as much as is humanly possible within the parameters of our policy -- which is no Americans and no American arms" involved in the conflict.

"The president has got to decide on a change," said Wilson.

Administration officials say they see no reason to change the present declared policy, which one said calls for "a complete withdrawal of Soviet forces within a fixed and reasonable length of time" and establishment of an Afghan government acceptable to the Afghan people.

They do admit, however, that the U.S. commitment to a negotiated settlement and interest in recent Soviet feelers about a possible withdrawal timetable have raised questions, at least in the minds of Afghan rebel leaders, about whether Washington might not be ready to sacrifice the resistance to a compromise.

Supporters here of the Afghan resistance say the administration should drop its ban on the provision of U.S. antiaircraft arms, citing this and the prohibition of direct U.S. arms deliveries as the chief obstacles to a more effective military aid program.

They argue that some kind of U.S. antiaircraft weapon has now become essential to enable the guerrillas to fend off the heavily armored Soviet helicopters that have become the bane of the resistance. Right now, the chief rebel antiaircraft weapon is the Soviet-made, heat-seeking SA7 missile.

Congressional and other sources close to the resistance say 10 Swiss-made, 20-mm Oerlikon antiaircraft cannons purchased for the rebels by the CIA are in use inside Afghanistan. Under pressure from Rep. Wilson, the CIA in mid-1984 reportedly set aside $40 million largely to buy 40 Oerlikons, according to these sources.

But critics argue the 750-pound weapon is proving difficult to assemble and disassemble and ill-adapted to mountainous guerrilla fighting, which requires quick movement. Many want the administration to provide either the U.S.-made Redeye missile or the British Blowpipe, both of which they say are superior to the SA7.

One congressional source and a U.S. official hinted that the administration may already have decided to provide the Blowpipe, but there have been no reports of any arriving yet on the battlefield.

As for direct delivery of arms, U.S. supporters of the guerrillas argue this would prevent either the Pakistanis or Afghan guerrillas themselves from skimming any off. One proposal is for C130 air drops inside Afghanistan.

U.S. analysts both within and outside the administration say the key problem in monitoring deliveries is that the CIA has few agents on the ground in Pakistan to oversee the program or to contact directly the individual guerrilla groups to assess their needs.

Administration officials dismiss the idea of air drops as too risky both for Washington and Islamabad and say direct U.S. management of deliveries is a political impossibility because Pakistan insists for security and other reasons on controlling the flow of arms through that country.

As for a full-time White House coordinator of aid to the Afghan resistance, Sens. Wallop and Humphrey and former national security adviser Zbigniew Brzezinski have proposed this, but they have received no response from the White House. "There is literally no one person of any authority spending all his time on Afghanistan in the administration," said Humphrey.

Administration sources said there is such a coordinator in Charles Dunbar, an aide to Assistant Secretary of State Richard W. Murphy. In addition, they said, Undersecretary for Political Affairs Michael H. Armacost chairs a Senior Interagency Group that has been set up to coordinate U.S. policy and programs toward Afghanistan.

Meanwhile, two conservative lobbying groups here for the Afghan guerrilla cause have launched a nationwide campaign to get CIA Deputy Director McMahon removed from office. They charge he has mishandled the U.S. covert aid program and made policy on his own by seeking to limit the quality of U.S.-purchased arms going to the rebels.

The organizations, Free the Eagle and the Federation for American Afghan Action, say the campaign begun in late October has resulted in 10,000 to 12,000 letters being sent to White House Chief of Staff Donald Regan complaining about McMahon's performance.

The form letter charges that McMahon has failed "to carry out effectively the Reagan administration's policy of effective aid to the Afghan freedom fighters" and asks that he either be dismissed or begin implementing the program better.

CIA spokesperson Patti Volz, while refusing to comment on any aspect of the agency's covert Afhganistan operation, said "any allegations that McMahon has mismanaged anything are absolutely assinine."

Volz said that McMahon had turned down a request to be interviewed.