Terror Threat Prompts Alert at U.S. Bases : Panama: Danger comes from drug cartels. Extra security causes massive tie-ups, delays for personnel.

Security has been tightened at all U.S. military installations in Panama because unidentified terrorists linked to the Latin American drug cartels have threatened to attack American targets there, Administration sources said Monday.

U.S. officials in Washington said that the threat, received a week ago, is being taken “very seriously.” They declined to be more specific, citing security concerns. The source and exact nature of the threat are “very heavily classified,” a senior Administration official said.

A Pentagon official said the threat originally targeted three U.S. military bases on the Pacific end of the Panama canal--Albrook Air Force Station, Howard Air Base and Ft. Clayton.

On Friday, however, the alert was broadened to include all military installations in Panama, where 12,000 U.S. personnel are stationed.

After a series of weekend meetings in Washington, including one at the White House, officials decided to continue the high state of readiness, citing an “ongoing” threat.

“Although no explosions have occurred, heightened security remains in effect at all U.S. defense sites,” a Defense Department official said Monday.

There is an “extremely serious evaluation of the threat being conducted by several U.S. agencies,” a federal source said.

Increased security measures led to massive congestion in Panama, where one military officer reported that it took him three hours to commute to work, normally a 20-minute trip.

Drug traffickers operating from Colombia have waged a long campaign of terror against police, prosecutors and public officials there.

U.S. officials said the current threats against U.S. installations are not linked to Panama’s military chief and ruler, Gen. Manuel A. Noriega. He is under indictment by grand juries in Tampa, Fla., and Miami on drug-trafficking charges and narrowly escaped a coup attempt in early October.

The U.S. Southern Command, based in Panama, oversees American military operations in Central and South America. Its commander, Gen. Maxwell Thurman, called for an all-out war on the drug cartels when he was sworn in Sept. 30.

“We must fight drug traffickers who threaten our families and our peoples,” Thurman said at that time.

Thurman was in Washington on Monday to testify before a closed session of the House Armed Services Committee on the subject of the U.S. presence in Panama and possible American participation in future coup attempts there.

President Bush and congressional oversight committees recently approved a new effort to overthrow Noriega, designating $3 million for a CIA-led effort to recruit Panamanian dissidents to topple the dictator.