Tribal areas of Pakistan and Afghanistan have become the major source of heroin for Western Europe, replacing the "golden triangle" of Southeast Asia.

These remote regions, rarely under government control and now near anarchy because of the open rebellion against Afghanistan's Marxist rulers, not only have become major suppliers to Europe but also are beginning to ship heroin to the United States.

According to U.S. State Department estimates, Afghanistan and Pakistan grow enough opium to produce 55,150 tons of heroin annually, and the amount is increasing steadily.

West Germany alone is believed to receive from these two countries 85 percent of its heroin, some of which finds its way to American troops stationed there.

"Significant quantities of Middle Eastern heroin [from Afghanistan and Pakistan] could possibly reach the United States by early 1980," said Peter Bensinger, administrator of the U.S. Drug Enforcement Administration, in recent Senate testimony.

"The growing Afghanistan and Pakistan opium surplus is clearly capable of supplying heroin to many markets beyond those in Europe, including the United States, which is being increasingly deprived of its supply from Mexico," added Mathea Falco, assistant secretary of state for international narcotics matters.

Because of the insurgency in the tribal areas of Afghanistan and political instability in Pakistan, international efforts have failed to establish substitute crops that would pay the farmers as much as they receive for opium poppies, according to authorities here.

Moreover, the instability here, in Pakistan and in neighboring Iran makes it easier to smuggle opium and morphine -- an opium product that is one tenth its bulk -- across borders.

The opium and morphine are moved by camel caravans, on the backs of donkeys and in the gaily painted trucks that ply the roads of these countries -- smuggling routes for thousands of years.

Recently Afghan police noticed a strong odor coming from a truck stopped at a roadblock. It was 80 pounds of tar-like raw opium -- worth $8 million on the streets of Frankfort or Washington in the form of heroin.

Although they have only a tenuous hold over much of the country, Afghan police are waging a vigorous attack on narcotics smuggling -- partially because of the strict attitudes of their Soviet advisers toward drugs and partially because corruption here has decreased, international narcotics agents here said.

Oddly enough, the war against heroin is one of the few areas where there is full cooperation between American and Afghan officials. One U.S. diplomat who usually dislikes visiting the forbidding Interior Ministry said the attitude of narcotics officers toward Americans is cordial.

"They invite us in, offer us coffee and let us take whatever samples we need to send back to the United States for testing. It's so different from the rest of the ministry," he said.

The Afghans obviously are proud of their drug law enforcement record. Earlier this year, they invited U.N. officials here to watch the burning of a room-sized pile of hashish. The fire smoldered for more than three days.

According to sources here, the Afghans seized almost 81,000 pounds of opium last year and they already have taken almost 10,000 pounds this year.

Narcotics officials here said the Afghans are beginning to find morphine -- the first product in converting opium to heroin -- indicating that factories to refine the opium have been established here.

Morphine, which is less bulky than opium and lacks the odor and tar-like stickiness, is far easier to smuggle.

For the first time this year, Afghan authorities reported seizing 22 pounds of morphine as well as raw opium. There were more than 13 pounds of morphine hidden in the truck, along with the 80 pounds of opium.

The poppies are grown along the open border between Afghanistan and Pakistan, where members of the Pathan tribe cross freely from one country to another. The raw opium is shipped southwest toward Iran and Turkey. According to narcotics authorities here, much of it is smuggled into Europe by thousands of migrant workers leaving Turkey to find jobs elsewhere, especially in West Germany, which has a growing heroin addiction problem.

Opium is readily availiable in country markets here and Pakistan. In Landi Kotal, just over the Afghan border in Pakistan, for example, opium is freely sold in an underground bazaar along with smuggled silk, perfumes and transistor radios.

"If you are what appears to be a legitimate buyer, you can conduct your business openly, but if you look like a narc, you are dead," said one enforcement official here.