U.S. Agents in Combat to Defend Base in Peru : Drug war: Americans and Peruvians fight off attacking guerrillas. No defenders are hurt.

The Bush Administration on Thursday reported the first combat involving U.S. personnel in the stepped-up Andean drug war, saying American agents and contract pilots helped beat back a midnight attack by Sendero Luminoso guerrillas on an anti-drug base in Peru.

In providing details of a fierce 85-minute clash, Administration officials stressed that the battle at the Santa Lucia base in the Upper Huallaga Valley was a “cost of doing business” as the United States seeks to boost its counter-narcotics effort overseas.

But critics, including Sen. John Kerry (D-Mass.), questioned whether the United States remains capable of protecting Americans dispatched to the base, in the heart of the world’s largest coca-growing region and near the center of one of its fiercest guerrilla wars.

Although the American and Peruvian defenders suffered no casualties, the armed attack early Saturday morning on their newly fortified joint headquarters underscored a particularly sensitive aspect of the Administration pledge to crack down on drugs at their source.

U.S. officials have sought for months in their public statements to prepare Congress and the public for the prospect that its drug war might well enmesh American agents in combat overseas. But the assault in Santa Lucia, apparently by guerrillas of a Maoist group whose name in Spanish means Shining Path, provided the first glimpse of the kind of hostilities that some have predicted will become more common.

In a planned “emergency” response to the attack, American civilian helicopter pilots took off from the base in UH-1H Huey gunships and flew over the attackers’ positions while Peruvian gunners used door-mounted M-60 machines guns to open fire on those below, according to accounts provided by U.S. officials.

At the same time, other Americans, including agents of the Drug Enforcement Administration, took up positions inside the base and returned automatic-weapons fire against what officials now believe was a well-armed unit of Sendero Luminoso guerrillas.

Peasants who live in the area later reported that a truck had carried away guerrillas killed or wounded in the attack. U.S. officials could not confirm whether there were any casualties among the guerrilla unit, which numbered an estimated 35 to 50.

But the British news agency Reuters quoted a Peruvian official as saying that intelligence reports, based in part on eyewitness accounts, indicate that about 60 out of an attacking force of 200 were killed and 70 wounded.

Among the defenders, the estimated 15 Americans were a small minority compared to the 120 Peruvian policemen stationed at the base. A DEA spokesman, Frank Shults, stressed that the Americans had “in every instance” followed the orders of the Peruvian commander on the scene.

The Americans on the scene included both DEA agents and civilian pilots employed by a State Department contractor, National Air Transport Inc., to fly anti-drug missions overseas. The three Huey helicopters that flew sorties against the attackers are State Department aircraft on loan to the government of Peru.

The surprise assault marked the first time that the guerrillas, who are believed to provide protection to drug traffickers, risked an attack at the base that is the single most-important outpost of American anti-drug operations overseas.

With the Upper Huallaga Valley now believed to produce about half the world’s supply of raw coca, the Santa Lucia base is the principal jumping-off place for missions aimed at eradicating the crops or destroying the nearby laboratories that convert the harvest into cocaine.

Concern about a mounting guerrilla threat forced the base to be shut down for much of last year. It reopened after its perimeter had been heavily fortified.

In the wake of the Saturday morning clash, U.S. officials expressed satisfaction at the ease with which American and Peruvian personnel repelled the guerrilla attack.

“We just think of it as a minor incident,” said Gene Bigler, a U.S. Embassy spokesman in Lima. “We’re very pleased with the way it came out.”

DEA spokesman Shults said the anti-drug operations at Santa Lucia will not be affected by the incident. “The perimeter is considered safe and secure,” he said.

Times staff writer William R. Long, in Rio de Janeiro, contributed to this story.