WASHINGTON -
When the Pentagon called out the Marines on Wednesday and dispatched them to Libya, it wasn't the first wave of an invading force.
Instead, the 50 Marines are part of an elite rapid-response team and they were sent to assess and reinforce security in Libya in the aftermath of the attack in Benghazi that killed the U.S. ambassador there and three other Americans.
Known as a Fleet Antiterrorism Security Team, or FAST, the team's role is to respond on short notice to terrorism threats and to bolster security at U.S. embassies. They operate worldwide, and the team that went is one of two that are based in Spain.
Administration officials who discussed the Marines spoke on condition of anonymity because they were not authorized to speak publicly about the military movements. The Marines arrived at the U.S. embassy in Tripoli, and there were no immediate plans for them to advance to Benghazi. Officials said they did not know how long the team might stay there.
A second Marine FAST element was standing by in Spain but had no orders to move, officials said.
The Pentagon also ordered two Navy destroyers to the Libyan coast. Officials said the ships, the USS McFaul and USS Laboon, which carry Tomahawk cruise missiles, did not have a specific mission, but they give commanders flexibility to respond to any mission ordered by the president. The officials spoke on condition of anonymity because they were not authorized to speak publicly.
Pentagon spokesman George Little said the U.S. military regularly takes precautionary steps when potential contingencies might arise in a given situation. He did not comment on ship movements.
U.S. embassies, particularly in major countries and in unstable or less secure nations, usually have a resident contingent of Marine security guards. Early indications were that there was no Marine security unit at the U.S. consulate in Benghazi. A consulate is a branch office in major cities outside the capital. These guards work under the supervision of the senior diplomatic officer at an embassy.
The main role of Marine security guards is to protect classified national security documents, according to the web site of the Marine Corps Embassy Security Group, which administers the security guard mission from a Marine base in Virginia. Their secondary role is to protect U.S. citizens and U.S. government property in the event of an emergency.
The Marines began their security guard mission in 1948. They are trained at the Marine Security Guard School.
In rare cases, the Marines send a Fleet Antiterrorism Security Team, or a portion of the team, to reinforce security at embassies. They were sent to Africa, for example, in response to the 1998 terrorist attacks on the U.S. embassies in Kenya and Tanzania. A FAST group also provided security aboard a Navy hospital ship in New York following the 9/11 attacks.
By ROBERT BURNS AP National Security Writer
