The U.S. government has for several years received, but declined to investigate, reports of heroin trafficking by some Afghan guerrillas and Pakistani military officers with whom it cooperates in the war against Soviet influence in Afghanistan, according to U.S. officials and Afghans.

Afghans, including mujaheddin guerrillas, have given U.S. officials firsthand accounts of heroin smuggling by commanders under Gulbuddin Hekmatyar, a guerrilla leader with close ties to the Pakistani military who until recently was the foreign minister of the guerrilla-declared, U.S.-backed Afghan Interim Government. Officers of Pakistan's military intelligence agency, Inter-Services Intelligence (ISI), protect and participate in the trafficking, according to the sources, who were interviewed in Pakistan and Washington.

While the lack of investigations has prevented the United States from pursuing legal action against any such drug suspects, the administration has tried to combat the trade in other ways. In one sensitive effort, senior U.S. Embassy officials in Pakistan met last autumn with a powerful mujaheddin commander, Nassim Akhundzada, and persuaded him to halt opium production in his part of Afghanistan in exchange for U.S. consideration of development aid for the area. The commander, who cut cultivation of opium poppies significantly, was assassinated in Pakistan last month.

Publicly, the Bush administration has conceded only that some mujaheddin commanders individually may condone opium production and has denied involvement by the Afghan Interim Government. U.S. and ISI officials declined to comment publicly on allegations of trafficking by Pakistani military officers. A spokesman for Hekmatyar, Nawab Salim, denied involvement in drug trafficking by his group or its commanders, over whom he said the leadership kept strict control.

Many reports of the heroin trade have been supplied by intelligence sources who are regarded by U.S. officials as generally reliable, and U.S. drug enforcement officials take the reports seriously.

Nevertheless, according to U.S. officials, the United States has failed to investigate or take action against some of those suspected in part because of its desire not to offend a strategic ally, Pakistan's military establishment. Also, since the Soviet invasion of Afghanistan in 1979, U.S. narcotics policy in Afghanistan has been subordinated to the war against Soviet influence there, especially under the Reagan administration.

Despite years of rumors and reports about drug trafficking by mujaheddin and ISI, "there has been very little debate" on the issue among the executive agencies responsible for setting U.S. policy, said a U.S. official who, like most of those interviewed, requested anonymity. "It has been terribly frustrating for the Drug Enforcement Administration and others {concerned about the heroin trade} to weave narcotics matters more closely into general policy" in Afghanistan, said a senior U.S. diplomat.

Afghans in Pakistan have given U.S. officials accounts of extensive heroin smuggling by commanders under Hekmatyar, who has received tens of millions of dollars in U.S. weapons and supplies over the years. ISI, which favors Hekmatyar over the other Afghan guerrilla leaders, has funneled the largest share of outside aid for the Afghans to Hekmatyar's Islamic Party.

According to these accounts, Hekmatyar commanders close to ISI run laboratories in southwestern Pakistan, buying raw opium gum brought over the border from Afghanistan and cooking it down into morphine and then heroin. The heroin is smuggled out via Pakistani airports and ports -- mostly those of the city of Karachi -- or via an overland route through Iran to Turkey, the Balkans and Europe, the sources said.

ISI cooperates in heroin operations, according to the Afghan accounts given to U.S. officials.

In Pakistan's southwestern province, Baluchistan, the Pakistani military effectively shares authority with tribal leaders. ISI and army officers control the few passable roads across the border from Afghanistan, notably the roads leading to the town of Rabat, a drug smuggling center in the southwestern corner of Afghanistan bordering on Iran and Pakistan.

The army registers travelers and inspects cargoes traveling on such roads and controls the border areas where the laboratories are located. ISI runs mujaheddin training camps in the Koh-i-Soltan region, near where the laboratories are concentrated, the sources said.

Afghans who travel frequently in Nassim's territory in Helmand province and U.S. officials said Nassim sent most of his opium south to the laboratories in southwestern Pakistan, where the Pakistani army and tribal leaders share local authority.

One Afghan who said he had seen drug operations told of a Pakistani policeman friend who complained that army officers sometimes forced police to release Afghans involved in the heroin trade after their arrests on weapons or other charges. The source said he had given such accounts directly to U.S. officials.

Baluchistan's governor, Mohammad Akbar Khan Bugti, a tribal nationalist often at odds with the Pakistani army, said in an interview that frontier guards, army officers and ISI all were involved in heroin and hashish smuggling from Afghanistan. "They deliver drugs under their own bayonets," he said.

Bugti said corrupt military officers had tipped off heroin manufacturers near Koh-i-Soltan about a raid last year that was assisted by the U.S. DEA. The raid turned up only a kilogram of heroin (2.2 pounds) after reports that large-scale manufacturing was underway in the area.

ISI's spokesman declined to comment on charges of drug involvement by the agency.

In addition to the direct reports of ISI involvement, a general picture of the operation -- drawn from U.S. government reports and interviews with U.S. drug enforcement officials and Afghans -- raises the question of whether such large-scale heroin producers could thrive without the awareness or cooperation of ISI. In 1989, Afghanistan was second only to Myanmar (formerly Burma) as a producer of opium, growing 650 tons, nearly all of which was intended for heroin manufacturing, a State Department report said.

More than 250 tons of that opium -- nearly three times the amount produced in Mexico last year -- was grown in Helmand province, where Nassim was responsible for most of the production. Nassim was referred to locally as the "King of Heroin" after he fought a two-year war with one of Hekmatyar's commanders for control of the region's opium fields, according to Afghans and U.S. officials. He was associated with a mujaheddin faction opposed to Hekmatyar.

Some Afghans interviewed said they had told U.S. officials of drug operations by Hekmatyar and agents of ISI, but said the officials seemed to ignore the information.

A U.S. official agreed that U.S. intelligence agencies and the State Department have avoided issues of corruption and drug operations -- especially where they appeared to implicate ISI. "I think that every year, when our intelligence priorities are formulated, that has been left aside," the official said.

U.S. officials acknowledged that the United States plays down reports of narcotics trafficking by ISI and the Afghan mujaheddin, saying this has been partly for lack of evidence and partly because of the political sensitivity of exposing illegal activities by allies of the U.S. effort to oust Afghanistan's Soviet-backed government. "You can't look at {the narcotics trafficking} in a vacuum separated from the overall policy," the official said.

Felix Jimenez, DEA's chief heroin investigator, praised the Pakistani government of Prime Minister Benazir Bhutto for increasing drug seizures and cooperating with U.S. interdiction efforts. But while U.S. officials credited Bhutto with good intentions, they said she lacked either the political will or the means to confront powerful drug interests within the military and in the largely autonomous tribes of Pakistan's western border region.

Selig S. Harrison, a senior analyst at the Carnegie Endowment for International Peace in Washington, stressed that involvement in drug corruption extends beyond ISI and throughout the military structure, which rivals Bhutto for effective control in Pakistan. "You have about 10 Noriegas . . . very high up in the military," Harrison said, referring to the ousted Panamanian ruler, "and it's difficult to name names."

The United States has told the mujaheddin it will give no help to those who trade in drugs, but officials acknowledged that the United States has only limited control over arms distribution, which is handled by ISI and partly funded by Saudi Arabia.

Last fall, officials said, the administration tried to cut Afghan opium production by negotiating with Nassim. Senior embassy officials in Pakistan proposed the talks to Washington after Nassim offered to halt poppy farming in exchange for money.

"There was a debate with . . . by-the-book people" in Washington, the official said. Washington feared that the negotiations might be seen as a violation of Bush's 1988 campaign declaration that he would "never bargain with drug dealers on U.S. or foreign soil," a reference to dealings by previous administrations with Panamanian strongman Manuel Noriega.

The embassy officials met three times with Nassim last fall to discuss poppy cultivation in his territory and turned down a request by Nassim for cash, reportedly as much as $2 million, in exchange for an effort to reduce opium production. The Americans told Nassim he had to prove his willingness to halt poppy production before any discussion of development aid for his area could begin, officials said. While one official said the U.S. made a hard promise of development aid in exchange for a halt in poppy cultivation, others said the promise was simply to consider assistance via a U.S. Agency for International Development (AID) program. Nassim apparently held to his agreement to halt poppy production. Three monitoring teams sent to the region in January and February by AID reported poppy production substantially down. As a result, the price of heroin reportedly tripled in the Baluchistan border areas this spring.

Nassim's decision drastically reduced the amount of opium available to the Baluchistan heroin labs allegedly controlled by Hekmatyar's commanders, and some Afghans have speculated that Hekmatyar ordered Nassim killed as a way of protecting his operation. An Afghan arrested at the scene of the killing has said he is affiliated with Hekmatyar, according to Afghans and U.S. sources. Others suggested that Nassim may have been killed in revenge for his military defeat of Hekmatyar's commanders in Helmand three years ago or for urging commanders in Afghanistan to break away from Pakistan-based leaders such as Hekmatyar.

With Nassim now dead, the Helmand opium valleys again are up for grabs. Afghans say the leading contenders are Nassim's brother, Mohammed Rasul, and commanders affiliated with Hekmatyar. Forces loyal to Rasul and Hekmatyar have clashed violently in recent weeks in southern Helmand, along the main opium routes, according to mujaheddin sources in Quetta, Pakistan.

Coll reported this story in Pakistan and Rupert in Washington.