"The Abu Nidal organization is the one that we would rate as having the highest potential," Baker said. A 1988 U.S. government report called Abu Nidal's group "the most dangerous terrorist organization in existence."
However, Baker said, the FBI has not changed its overall assessment that terrorist attacks in the United States are much less likely than in Europe or the Middle East. "We continue to see a rather low level of activity within the United States," Baker said.
According to Robert Kupperman, a terrorism expert with the Center for Strategic and International Studies, the "infrastructure" for a terrorist organization consists of people who would supply safe houses, weapons, false documents and other assistance.
The Abu Nidal group, a radical Palestinian faction, was responsible for the 1985 machine-gun attacks on passengers at the Rome and Vienna airports. The group recently made direct threats to strike against American interests after the Justice Department extradited one of its members to Israel.
Asked why the FBI has not moved against Abu Nidal supporters in this country, spokesman Mike Koran said the agency cannot act unless a crime has been, or is about to be, committed.
Kupperman said New York, Los Angeles and Dearborn, Mich., which has a large Middle Eastern community, would be likely places for the Abu Nidal group to have a network.
Baker said the FBI was also concerned about threats from Hezbollah, the Iranian-backed group responsible for the 1983 bombing of the Marine barracks in Beirut.
"We expect that their actions would transcend any neutrality that Iran might maintain in this current war," Baker said.
FBI officials say they have confidence in the counter-terrorism program they developed and put in place during the 1980s, which includes working closely with state and local law enforcement agencies. FBI officials point out that while terrorist attacks on Americans overseas have been rising in recent years, incidents in the United States have declined.