"We can't show you the missiles here in the shop," said Gul, a Pakistani arms dealer, "but I could take you to where we keep them. Do you have money with you?"

Gul does not run an ordinary gun shop. His dimly lit single room opening onto Dara's only street was crammed with automatic assault rifles, machine guns and grenade launchers. The heavy barrels from disassembled artillery pieces lay jumbled up with boxes of ammunition and old bolt-action rifles.

But to see the best items, the Chinese-built 107-mm, surface-to-surface missiles, the customer must have money to show Gul (not his real name) that he is serious.

Gul would not say exactly where he and Dara's dozens of other arms merchants get the heavy weapons they sell, most of them Chinese-made. Instead, his suspicions aroused by the questions of my Afghan translator, he asked us to leave.

While the Pakistan frontier region is notorious for its indigenous arms-manufacturing, there is clear evidence that many of the weapons being sold in Dara -- and other arms markets nearby -- come from CIA-funded arms shipments meant for the Afghan mujaheddin or resistance fighters, opposing the six-year-old Soviet occupation of their country. Observers also believe China is supplying some weaponry to the guerrillas.

Last spring, U.S. congressional intelligence committees reportedly approved $470 million for covert military aid to the Afghan resistance for this fiscal year, and there were reports that Congress later approved a supplemental $300 million in assistance for two years, according to congressional and other sources in Washington.

But at best, resistance sources and military specialists say, the covert aid operation, administered by the CIA, lacks accountability and often delivers inappropriate arms. At worst, it may be losing substantial percentages of its shipments to corruption and contributing to a militarization of the volatile Pakistani-Afghan border area, which could ultimately help destabilize the United States' ally in the region, Pakistan. The Arms Pipeline

It is here, among the parched hills of Pakistan's tribal territories, that the pipeline ends. Dust-covered trucks roll into guerrilla bases along the Afghan border and unload arms to be cleaned and repacked on donkeys and horses for the trip into Afghanistan.

Accounts pieced together from Afghans, Pakistanis and westerners said that the CIA secretly buys weapons -- in China, Egypt and elsewhere -- and ships them to the Pakistani port of Karachi and isolated points along the coast of Baluchistan, to the west. One source said shipments in recent months included 40 tons of Soviet equipment captured by South Africa.

Once the shipments have landed, Pakistan's joint military intelligence agency takes over, transporting them to the Pakistani military installations for distribution to the mujaheddin. Pakistani military personnel advise each Afghan resistance group when to go to a particular depot to collect arms and then notify police of the truck's route to the group's base to avoid searches along the way.

According to two westerners who visited different bases in recent months, up to 70 percent of the weapons were Chinese, along with some Soviet and Egyptian-made arms. They included Kalashnikov assault rifles, rocket-propelled grenades, mortars, land mines and missiles -- many of them the same models as those on sale in Dara.

Mujaheddin and western observers in Pakistan say Pakistanis and Afghans are stealing weapons along the arms pipeline.

Independent western observers believe the Pakistani military is diverting entire batches of weapons for Pakistan's own use. They say Pakistani police officers have been issued new weapons in recent years -- such as Lee-Enfield Mark Five and Chinese-made SKS rifles -- which had come through the pipeline.

A source close to the Pakistani Army denied the allegations, saying the rifles had come from old Pakistani military stocks.

Many mujaheddin alleged that Pakistani officers who run the pipeline are often corrupt, demanding bribes or a portion of the arms shipments, which they later sell.

"The worst thing is that some who are stealing are Afghans," said Ezim Wardak, a resistance official in Peshawar, Pakistan. "They call themselves mujaheddin but they are really businessmen, trying to make a profit from the jihad," or holy war. A guerrilla leader from northern Jozjan Province said he and other commanders regularly sold some of the weapons they received in Pakistan as the only way of paying the increasing costs of transporting the arms into Afghanistan -- especially to its north and west. Pakistani Control --------

A Pakistani military analyst insisted that Pakistan's Army was not diverting weapons. "Those chaps the mujaheddin are a bit sore at us because we have certain controls over the weapons," he said.

Without giving details, the analyst explained that the Pakistani military often stores the arms, waiting for "the right time and the right groups" to distribute them.

Mohammed Es'Haq, a political officer of the Jamiat-i-Islami, conceded that some Afghan resistance officials are selling donated arms. Although his own party has an accounting system for the weapons, he said, "We don't have all the control we would like because we are guests here in Pakistan; we cannot run our own police force."

Es Haq and other resistance officials were reluctant to discuss the loss of arms from the pipeline, for fear publicity about the problem might prompt Congress to stop funding the operation. "It is better for us to get half of the weapons than to get none at all," said a guerrilla commander who asked not to be identified.

Despite the nearly universal allegations of corruption, it is unclear exactly how many of the CIA-supplied arms are being diverted. Different persons interviewed varied widely in their estimates and seemed to have little hard information.

Guerrilla commanders in Afghanistan, angry at having received few or no arms, argued that as much as 85 percent of the weapons are diverted, while Pakistani sources insisted that only a negligible amount is stolen -- and only by Afghans, never by Pakistanis. In fact, the secrecy of the pipeline, and the fact that the weapons pass through so many hands, may prevent anyone -- including the CIA -- from knowing what percentage of the weapons is lost.

Noting reports that Congress authorized $250-$280 million to run the secret arms operation in 1985, a western military specialist who has traveled regularly in Afghanistan with the mujaheddin said, "These figures are completely out of line with what the mujaheddin are seeing."

Formally, Pakistan denies the very existence of the arms-supply operation. But Pakistani officials admit openly that they are worried about the heavy flow of arms into the tribal territories where the pipeline ends.

In the latest episode of a historical tussle between Afghanistan and Pakistan for the loyalties of the Pushtun (or Pathan) tribes that straddle their border, the Afghan government has armed dissident tribesmen from the Pakistani side and encouraged them to oppose the mujaheddin and the Pakistani government.

In early December, Pakistan sent thousands of troops into the Khyber district to crack down on the Kabul-supported dissident tribesmen and seize what it claimed were more than a thousand Kalashnikov rifles and other weapons.

Western diplomats and others contest Pakistan's claim that the arms that flood markets such as Dara -- and the homes of Pushtun tribesmen -- are all sent by Kabul. "Why would the Afghans be sending Chinese arms, and where would they get them?" a western analyst in Islamabad asked.

So many weapons have poured into the area since 1980, when the CIA operation began, that the market price of a Chinese-made Kalashnikov has fallen by more than a third. The flow of arms has seeped into other areas; tribesmen in Baluchistan, bandits in southern Sind Province and even Sikh extremists in the Indian city of Amritsar have been reported using guns from the CIA pipeline.

"The Americans and Pakistanis could tighten the accountability of their operation. They could mark the arms when they ship them in, and then seize them when they turned up in the bazaars," said a western military specialist on Afghanistan. "They would be able to trace the diversion to its sources."

Many rebel commanders and others agreed with Shah Mohammed, a guerrilla chief from Logar Province who argued that outside arms donors should bypass the Afghan political parties and deliver the aid directly to proven commanders inside Afghanistan, as do many European organizations offering humanitarian aid. Afghan political leaders traditionally have distributed largesse to their clients and supporters as a way of gaining influence -- a habit that party leaders have continued during the war.

"The parties -- some more than others -- distribute the weapons to get political influence rather than according to the military needs of the jihad," Mustafa Wardak, a commander in Ghazni Province said.

The concerns about Pakistani and Afghan corruption are not limited to military aid. Officials of private aid organizations in Peshawar express misgivings about a new U.S. Agency for International Development humanitarian aid program preparing to spend $15 million this fiscal year on projects inside Afghanistan.

Like the military pipeline, the humanitarian aid operation will channel its funds exclusively through the Pakistani authorities and the Afghan political parties -- a structure that aid workers say invites corruption and inefficiency. The aid official questioned whether the necessary infrastructure exists inside Afghanistan to spend the AID money efficiently, which dwarfs their private efforts.

AID has not yet released details on how it plans to spend the money, but one western source in Islamabad, Pakistan, dismissed the aid workers' fears, saying AID was planning "some creative new ways" to use the money in helping the mujaheddin. 'Can You Read This?'

In the narrow ravine of their guerrilla base, the mujaheddin pried open wooden crates containing the Chinese missiles they would fire that night at Soviet positions in Ghazni. Inside one of the crates they found a sheet printed in Chinese and covered with tables of figures.

As he examined it, a guerrilla said, "I think it is information on how to launch the missiles." Suddenly, his face brightened, and smiling, he handed the paper to a Japanese photographer who had come to cover the war.

"Can you read this?" he asked.

The incident symbolized what many mujaheddin regard as one of their most basic problems in this war: their lack of technical information and training in how to use their weapons.

Whatever its problems with corruption on the Pakistani side of the border, the CIA's arms pipeline has succeeded in delivering the heaviest and most sophisticated weapons the resistance has had during its six year battle against the Soviets.

"Unfortunately, these weapons are coming to men who are illiterate peasants . . . and they are not being taught how to use them," said an American military specialist who has traveled with the mujaheddin.

At the few drab restaurants and hotels in Peshawar favored by foreign visitors, western journalists and others who have accompanied the mujaheddin inside Afghanistan recount stories about guerrillas firing missiles without detonators, planting land mines upside down and -- one of the most consistent observations -- wasting ammunition in small and ineffectual attacks on Soviet posts.

"Most of the mujaheddin . . . find the range with a mortar by setting it up, firing off a few rounds and tinkering with it," said Peter Jouvenal, a British documentary film maker who has covered the war since it began. "By the time they're ready to hit the target, they've run out of ammunition."

"If the CIA or anyone else were serious about helping the Afghans, they would be training them," one military analyst said. "westerners have this idea that the Pathans the largest Afghan ethnic group are natural fighters, and to an extent that's true," he said, "but you cannot expect a farmer to aim a modern missile with his instincts."

Several sources said the Pakistani Army had run -- and apparently stopped -- a small-scale training program for the mujaheddin, in addition to rudimentary training by the parties based in Peshawar.

Several military observers said the delivery of even simple forms of aid to the mujaheddin could be dangerous to the guerrillas in the absence of training. One described mujaheddin who received radios but who knew nothing about codes and broadcast their movements to each other in plain language.

Military specialists who have traveled with the mujaheddin argued that training would not only improve how the guerrillas handle their weapons but would help overcome divisions among guerrillas of different parties and regions, and improve their cooperation in the field.

Many, but not all, commanders agreed on the need for training. Several commanders from the fundamentalist Hezb-i-Islami faction of Gulbuddin Hekmatyar argued that military training, like secular education, was of relatively minor importance, next to the religious faith of the mujaheddin.

"It is the man and his faith which fights," said Shamsuddin, a former medical student now commanding a Hezb-i-Islami guerrilla group in Kunduz Province, in the north. "If training were most important, the Soviets would have beaten us long ago, because they have training and we do not," he said. Air Defenses Critical

"We heard you are an American," the middle-aged guerrilla said. For 40 minutes, he and a companion had sat silently, on the floor of the teahouse, watching closely as I scribbled notes from the day's long hike.

That now finished, the men explained their request:

"When you go back to America," one asked politely, "could you send us some air defense?"

Although the question sounded odd to an American reporter, for the two Afghans it was both serious and urgent. Indeed, during a month inside Afghanistan, numerous guerrillas stressed that their greatest need in military aid is a defense against the Soviet jets and helicopters that attack their supply caravans and support commando raids against them.

The mujaheddin have little effective air defense, relying on heavy machine guns and a limited number of Soviet-made SA7 missiles. Virtually all the mujaheddin encountered disagreed with the conclusions of a December State Department report that said that resistance air defenses had improved with growing numbers of surface-to-air missiles and reduced the effectiveness of Soviet air power.

The most important recent change in the air war, according to Kabul area commander Abdul Haq and others, is that the Soviets now use more helicopters, especially in commando operations.

"They used to send in seven or eight helicopters in an attack, but now they might send 20," he said. The mujaheddin have responded, he said, by offering smaller targets. "We have to move our supplies at night, we use smaller caravans -- maybe with 20 camels instead of a hundred."

Many mujaheddin believe that more and better missiles are the answer. And in Washington last fall, intelligence sources were quoted as saying the Reagan administration was considering supplying sophisticated portable antiaircraft missiles, such as the British blowpipe system.

"The U.S. must be careful about listenening to missile requests," a western military analyst said in Peshawar. "The mujaheddin see solutions to their problems too easily in sophisticated hardware."

The analyst said that much of the reason for the guerrillas' disappointment in the antiaircraft missiles was their lack of training.

He suggested that simpler weapons, such as Soviet wire-guided missiles would be easier for the mujaheddin to learn to use.

"If they're thinking of sending in even more sophisticated weapons, without any training program, I wonder if they really know who they're dealing with," he said.