The turnover of a U.S. military base to Panama earlier this month has left a gaping hole in American counter-drug efforts in Central America and the Caribbean, forcing the Clinton administration to scramble for new facilities that can be used to track drug shipments from South America.

All U.S. forces are scheduled to leave Panama, formerly headquarters for the U.S. Southern Command, by the end of the year under terms of the Panama Canal treaties. On May 1, Howard Air Force Base was turned over to Panama, depriving the United States of a base for 22 surveillance aircraft and causing a sharp drop in anti-drug coverage of the region.

To maintain a presence in the area, the Clinton administration has hastily negotiated a short-term agreement with the Netherlands to station aircraft at the airports in the Dutch Caribbean protectorates of Aruba and Curacao. It negotiated a similar agreement with Ecuador to station airplanes in the Pacific coast city of Manta.

Washington is seeking a third such agreement in Central America and, to that end, is currently negotiating with Costa Rica. All of the new airfields, however, will require substantial improvements -- including new maintenance facilities and housing -- that will cost more than $100 million, Pentagon officials said.

U.S. aircraft flew about 2,000 surveillance missions out of Howard last year, gathering intelligence for the United States and for counter-drug forces in other countries in the region, officials said. Pentagon officials said that even under ideal circumstances it will take two to three years to regain the surveillance capability that existed in Panama.

All the cocaine and most of the heroin used in the United States is produced in South America and moved north by airplane or ship through Central America and Mexico or through the Caribbean.

In a May 20 letter to Defense Secretary William S. Cohen, four Republican congressmen warned that the loss of Howard has presented the United States with "one of the worst disasters in our U.S. counterdrug history."

"These counterdrug flights are essential for information sharing with other countries in the region, for eradication and narcotics interdiction," said the letter from representatives John L. Mica (Fla.); Benjamin A. Gilman (N.Y.); Mark Edward Souder (Ind.); and Robert L. Barr Jr. (Ga.). "Without these essential flights the department is creating a wide open door to drug traffickers and destroying the first line of defense against illegal narcotics traffickers."

The letter said that "failed negotiations" with Panama and "the absence of adequate advance planning" had endangered the drug war.

Barry R. McCaffrey, the administration's national drug policy director, said he was "worried" by the loss of Howard but blamed the delay in getting the new bases operational on then-Panamanian President Ernesto Perez Balladares, who, he said, had agreed privately to extend the U.S. presence in Panama, then backed out last September.

"I'm very disappointed," McCaffrey said. "It has put us in a scramble."

Ana Maria Salazar, deputy assistant secretary of defense for drug enforcement policy, said at a congressional hearing May 4 that the Pentagon could not approach other countries about hosting U.S. surveillance aircraft until after the talks with Panama formally ended. This left very little lead time to put other agreements together, she said.

The opening of the centers in Aruba and Curacao will eventually allow the United States to fly about 65 percent of the surveillance missions flown out of Howard last year, Pentagon officials said. That level will increase to 110 percent following the opening of the center at Manta and a third location in Central America, the officials said.

The agreement with the Netherlands runs through September, and the agreement with Ecuador expires next May. But U.S. officials expressed confidence that the host countries would agree to long-term arrangements because each of the new locations would require only eight U.S. soldiers, although that number would fluctuate as air crews rotate through the bases on temporary assignments.

"We think we have a good strategy," said one Pentagon official. "While the arrangement is different, it's a more productive way of engaging other countries."