U.S. antidrug efforts have made virtually no headway in disrupting cocaine trade in Peru and Bolivia, in part because Drug Enforcement Administration operations have been repeatedly undermined by corruption in the armed services of both countries, according to a congressional study.

The study by the the House Government Operations Committee concluded that the DEA should avoid further risk to its agents and "redirect" its efforts away from paramilitary-style antidrug raids in the Peruvian and Bolivian jungles.

The report, scheduled to be released today, is the latest congressional study to raise questions about Operation Snowcap -- DEA's 3 1/2-year-old program of dispatching U.S. drug agents to lead local police on strikes against clandestine airstrips, processing facilities and other drug-trafficking operations.

Last May, a senior DEA official said the agency would begin a "phased withdrawal," but recently DEA officials have strongly defended the operation, saying U.S. participation in the raids will continue for the indefinite future.

DEA spokesman Con Dougherty said Friday the report's findings were out of date in light of recent evidence that the flow of cocaine from Latin America has dwindled sharply in recent months. "We do have indications that the availability of cocaine in the United States is down . . . and the price is up," Dougherty said. "I think we can safely call this a trend now, and a lot of this has to go back to the efforts that are being made in Snowcap. . . . If it ain't broke, don't fix it."

But Rep. Robert E. Wise Jr. (D-W.Va.), chairman of the Government Operations subcommittee on information, justice and agriculture, which prepared the report, said recent progress is almost entirely due to the antidrug crackdown in Colombia launched last year by former president Virgilio Barco, and is not the result of any DEA operation.

"It is ironic that in Colombia, where there are no Snowcap agents in the field, interdiction operations have been quite effective," Wise said.

Despite the public attention to Colombia's attack on the leaders of the Medellin cartel, more ominous developments are occurring in Peru and Bolivia, the report said.

It noted a continued increase in the size of the coca crop, the raw material used to make cocaine. It also challenged the value of any increase in training and aid for the Peruvian and Bolivian military forces, a cornerstone of the Bush administration's Andean antidrug strategy.

The report called drug-trafficker corruption within both militaries "endemic." During two antidrug raids in Peru earlier this year, DEA agents and Peruvian police were stoned by local peasants led by Peruvian military personnel, the report said. In two other instances in March, State Department helicopters were fired on by Peruvian military officers when they approached drug-trafficker facilities.

Major processing facilities and airstrips in Peru's Upper Huallaga Valley -- the country's main coca-growing area -- are located near Peruvian military facilities to provide them with greater protection, according to a senior DEA official quoted by the subcommittee staff.

The report cited similar problems in Bolivia, including one instance in which the Bolivian Navy fired on U.S. helicopters and another in which traffickers were tipped off in advance about a major raid involving 30 DEA agents. The United States "receives almost no cooperation from the Bolivian Army, Navy or Air Force in the conduct of narcotics interdiction operations," the report said.

While the Andean strategy calls for $33.7 million in aid to the Bolivian military this year, the report quotes senior U.S. officials as acknowledging that "there is no guarantee that all, or any part, of the assistance . . . will be used for narcotics control purposes."