The buildings housing U.S. embassies in Israel and Yugoslavia are dilapidated and highly vulnerable to spies and terrorists, according to a new congressional report and a State Department official.

Both embassies are in potentially dangerous regions, the sources said, noting that terrorists often try to attack targets in Israel and have been allowed to operate freely in Yugoslavia and other Eastern European countries.Deputy Assistant Secretary of State Richard Dertadian said in an interview that the two missions, along with the one in Moscow where security problems previously have been disclosed, are likely the most deteriorated U.S. embassies in the world.

Dertadian was reacting to an unreleased March 11 report from a congressional delegation led by Rep. Olympia Snowe, R-Maine, the ranking Republican on the House Foreign Affairs subcommittee on international operations.

The report, a copy of which was obtained by United Press International, blasted the State Department office headed by Dertadian for failing to upgrade the Belgrade, Yugoslavia, facility in the past few years.

The report termed the embassy in Yugoslavia "a dilapidated, structurally unsound firetrap" that "poses a clear threat to the safety, security and morale of Embassy personnel."

A Foreign Affairs Committee aide who helped write the report said frequent breakdowns of electrical, heating and cooling systems at the Yugoslav facility force repairs that leave gaps in the structure.

Securing the building "is like trying to plug up Swiss cheese," the aide said.