After more than a year of intense debate over its operations in Latin America, the Drug Enforcement Administration has decided to scale back its role in a controversial paramilitary campaign aimed at disrupting the flow of cocaine from the Andean countries, according to agency officials.

DEA will begin a "phased withdrawal" of its agents assigned to accompany Peruvian and Bolivian police units on raids against clandestine laboratories, airstrips and other drug trafficker hideouts as part of Operation Snowcap, as the program is known, agency officials said.

The move comes amid heightened concerns within the Bush administration about the safety of Snowcap participants, particularly in Peru's war-torn Upper Huallaga Valley, where about 10 DEA agents and 20 State Department contractors are stationed at a heavily fortified military base at Santa Lucia.

Two months ago, the base was attacked by Shining Path guerrillas using rocket-propelled grenades, provoking a two-hour firefight in which some American pilots reportedly participated. There were no U.S. casualties.

But Stephen H. Greene, assistant DEA administrator for operations, denied the move to scale back Snowcap was primarily the result of security concerns. Instead, he said, it reflected DEA's conclusion that it could slowly begin turning over supervision of narcotics raids to local forces.

The idea is "to assist those host countries in order that they can be self-sufficient and run those operations, those patrols, strictly on their own," Greene said. "Our commitment {to Snowcap} hasn't waned at all."

For the past 2 1/2 years, DEA has dispatched teams of agents -- about 30 at a time -- for two- to three-month assignments with Peruvian and Bolivian narcotics police. Although DEA originally planned for its agents to serve as advisers, the agents quickly assumed an "operational" role and have actively participated in most raids, according to officials familiar with the program.

The agency's plans call for phasing out these Snowcap assignments over the next two years, Greene said. At the same time, he added, these agents will be replaced by DEA agents on "permanent" assignment for two to three years, but they will not go out on raids.

U.S. officials acknowledge that these and other U.S. anti-narcotics plans in the region are uncertain, especially in Peru as a result of the election this week of Alberto Fujimori as president.

In comments after the election, Fujimori said he did not believe there is a need for "external forces" to conduct anti-drug operations in his country and indicated he may not sign a new $36 million military aid package proposed by the Bush administration to prod the Peruvian armed forces into taking a more active role in the drug fight.

"Nobody knows anything about Fujimori," said one State Department official. "There's great uncertainty about what he's going to do."

The decision to revamp Snowcap represents a major policy shift for DEA and follows considerable dissension within the agency. Snowcap was conceived in late 1987 and agency officials initially contended it could cut the flow of cocaine to the United States in half within a few years.

But the program has been plagued by repeated difficulties. Agents complained about widespread corruption among the Peruvian and Bolivian narcotics police. In a 1988 memo, Frank E. White, chief of DEA special training, charged that agents were not being given adequate support for their mission, warning that without immediate changes, "DEA agents are going to agonize along through an excruciating death on an isolated jungle floor."

Since then, DEA officials said, they have expanded jungle-warfare and Spanish language training for agents. But in a memo to all agents written shortly before he resigned last March, Administrator John C. Lawn wrote that volunteers for Snowcap were "dwindling" because agents were not being offered sufficient promotion credits for entering the program.

Lawn increased those credits and Greene said this was a "tremendous morale booster." He also said there has been "substantial progress" in interdicting the flow of cocaine from Peru and Bolivia in recent months and that "we are starting to see some positive indicators" in terms of lowered purity and higher prices for cocaine.