Using U.S.-supplied radar tracking data, Colombia and Peru have resumed a policy of shooting down planes suspected of smuggling narcotics, and a U.S. Army general said the practice has seriously disrupted the cocaine pipeline.

In the past four months, 17 airplanes have been shot out of the sky or forced to land by Colombian and Peruvian warplanes, said Gen. Barry R. McCaffrey, chief of the U.S. Southern Command based in Panama.Gen. McCaffrey said he wasn't sure how many of the 17 planes had been fired on while in flight, but that "both Peru and Colombia have shot down aircraft."

The United States suspended anti-drug operations with the two Andean nations in May 1994, out of concern that U.S. officials could be held liable under international law if Colombia or Peru used the U.S. radar data to shoot down the wrong aircraft.

Gen. McCaffrey said those concerns have been overcome and the U.S. military is again supplying intelligence that allows the Andean air forces to pursue, pinpoint and fire on flights suspected of carrying drugs.

Strict guidelines are in place to ensure that only smuggling flights are targeted, he said.

"They are being scrupulous to obey their own laws and the international aviation conventions. There have been no mistakes," he said.

U.S. concern over knocking down civilian aircraft in error led the Defense Department to close ground-based radar stations in the Peruvian and Colombian jungles on May 1, 1994.

Colombia has two U.S.-operated radar stations in its Amazon region, and Ecuador and Peru have one each. Their exact locations are secret. The radars monitor flights coming from an Amazon region where most of the world's coca is grown. The leaf from the coca plant is the raw material for cocaine.

Peru and Colombia say the shoot-down strategy is essential to halting the flow of cocaine across the vast expanses of the Amazon jungle toward the north. Without U.S. radar data, they would not be able to hunt down drug planes.

After the radar facilities were closed last year, Congress passed a law requiring that the Clinton administration certify that countries receiving intelligence and radar data take measures to protect against innocent loss of life.

President Clinton certified that Colombia had taken such steps Dec. 1 and that Peru had done so "very recently," said Maj. Terry Farrell, a lawyer for the U.S. 12th Air Force.

Pilots attack only after determining that the suspected aircraft has filed no flight plan, is ignoring radio calls and refusing to respond to visual signals - such as the bobbing of wings by adjacent aircraft - to land immediately, U.S. military officials said.

As a final gesture, the tracking aircraft fire tracer bullets near the

suspect plane that light up the sky and give the pilot a visual warning, Gen. McCaffrey said.