In the first known operation of its kind, six U.S. Army helicopters are scheduled this week to begin airlifting Bolivian police in a series of raids on cocaine-processing facilities in Bolivia.

The operation appeared to mark a precedent-setting use of U.S. military resources for a drug-eradication operation in a foreign country -- reportedly causing friction between Defense Secretary Caspar W. Weinberger, who had resisted American Army involvement, and Vice President Bush, who urged the military action as chairman of an antinarcotics task force. President Reagan approved a secret directive April 8 authorizing the use of military force in such operations. Details on Page A18.

Coordination of the drive also represents a bold decision by Bolivian President Victor Paz Estenssoro to go after narcotics traffickers, who have enjoyed a large degree of freedom in this South American country.

U.S. and Bolivian authorities had tried to keep the operation secret until the raids started. But Bolivian newspapers this afternoon carried front-page reports of the landing yesterday in the city of Santa Cruz of a U.S. C5A cargo plane, which unloaded six Black Hawk helicopters, and of a C130 carrying trucks, jeeps, radio equipment and field gear for a camp installation.

The stories, published in Santa Cruz and here in the capital, heralded the start of what one paper called an "antidrug operation on a grand scale."

The Bolivian press reports removed the element of surprise that drug enforcement officials had been hoping to maintain and seemingly reduced the likelihood of the raids netting any major traffickers. But the operation, which is understood to be targeting large and sophisticated cocaine-processing laboratories set up in growing numbers recently in central and northern Bolivia, could still have a substantial impact on this country's extensive drug trade.

The U.S. Embassy this afternoon released the following statement: "U.S. helicopters and U.S. personnel have been sent to Bolivia at the request of the Bolivian government to provide transportation support to Bolivian civil authorities."

About 140 American military personnel are said to have arrived in connection with the operation, mainly to provide support services. The helicopters, dispatched from U.S. Army Southern Command Headquarters in Panama, reportedly are to be flown by U.S. as well as Bolivian pilots. But the actual strike force, according to informed sources, will be all-Bolivian teams drawn from a 650-man antinarcotics police unit. The unit has been trained, clothed and fed -- and its vehicles provided -- with U.S. funds.

Bolivia, a poor nation of 6.4 million people in South America's center, is estimated to supply about one-fourth to one-half of the world's coca paste, the extract from coca leaves that is refined into cocaine crystals. Despite a signed commitment in 1983 by Bolivian authorities to eradicate thousands of acres of coca leaves, illegal cultivation has spread, along with an expansion in the wealth and influence of Bolivia's traffickers.

Informed sources said that fear of the traffickers' growing political power is one of the main factors that motivated Paz Estenssoro to approve the joint strikes. Other concerns of the president, according to persons who have discussed the issue with him, are the surge in drug abuse among Bolivian youth and the threat to legitimate domestic commercial operations posed by the import of cars, tractors, planes and other goods, with narcotics money, for resale here as a means of laundering profits from the drug business.

Nevertheless, the willingness of the 78-year-old Bolivian leader to authorize a U.S. military presence in his country -- if only for the month or two that the operation is scheduled to last -- is expected to leave him vulnerable to political attacks.

Politics are already tense as a result of the government's economic austerity program. Moreover, some here say that any attempted crackdown on drug barons would expose government officials to violent counterattack.

For its part, the Reagan administration had to overcome the Defense Department's traditional reluctance to permit the use of military equipment and soldiers in foreign drug operations.

Intelligence gathered by U.S. Drug Enforcement Administration officials pinpointed months ago numerous processing facilities in Bolivia, but authorities here lacked the means to stage air strikes against them. All four of Bolivia's battered Bell Model 205 copters have been out of service since December, and the State Department's International Narcotics Control Bureau's budget, about $60 million for operations worldwide, cannot afford to purchase or usually even rent troop-transport helicopters for Bolivia.

Bush, who heads the National Narcotics Border Interdiction System, is reported to have countered Weinberger's objection to the deployment of the U.S. craft and personnel to Bolivia. In a June 9 statement, a spokesman for the vice president foreshadowed this week's operation, saying the administration expected to increase military action against drug trafficking.

A DEA official, speaking before Washington received word of the Bolivian newspaper accounts, said that any premature release of information about the operation would destroy extensive DEA work in pinpointing some of the most strategic drug-processing laboratories and transshipment points. He said that revelation of the planned raids would result in the cocaine and processing supplies being moved before authorities could complete the operation, Washington Post staff writer Mary Thornton reported.

According to a federal official, the helicopter-borne raids were postponed twice because of "logistical" problems involving the C5A ferry flight. The official said that the U.S. government had decided the plane should be moved out of Bolivia before the operation started because of the likelihood of an attack against it by angry drug traffickers.

The first problem arose last Friday when a wildcat gasoline strike prevented refueling of the C5A, which required 20,000 gallons for the trip. The official said a second postponement, Tuesday, was ordered after a logistical problem was discovered involving either a minor repair or a problem with the runway length.

A U.S.-Bolivian pact signed in 1983 and due to expire next month spelled out an agreement pumping millions of dollars in narcotics control and rural development money into Bolivia in exchange for the eradication of a portion of what was then estimated to be about 100,000 acres of coca leaf production.

But very little has been eradicated, and $7 million in U.S. economic support funds earmarked for Bolivia have been withheld this year because of this country's failure to realize eradication goals. Rather than decrease, coca-leaf cultivation has expanded in the Chapare region, a vast fertile swatch of the western Amazon as big as New Jersey, while suspected traffickers arrested with U.S. assistance have slipped easily through Bolivia's porous judicial system.

Moreover, the number of elaborate processing facilities for refining coca paste has multiplied in what U.S. experts say reflects a vertical integration of narcotics production by the country's 25 or so major illicit drug organizations.

This burgeoning narcotics trade is blamed in part on a combination of underequipped law enforcement teams and official complicity with the drug barons. But U.S. officials have acknowledged some misdirection of the campaign through overemphasis on eradication and not enough on interdiction of laboratory facilities and transport of narcotics from the sources of production.