Soldiers from the United States national guard are being sent to protect US bases in the UK in the event of a war against Iraq.
The US national guardsmen will check vehicles
Troops will be sent to RAF Lakenheath and RAF Mildenhall in Suffolk and RAF Molesworth in Cambridgeshire.
These are officially RAF stations, but are run and occupied by the US Air Force.
A spokesman for the US airforce told the Air Force News Service more than 300 soldiers will be involved and the first troops will be from the Puerto Rico national guard.
The spokesman said the soldiers would free up manpower shortages caused by possible action in the Gulf.
The soldiers will search vehicles at the bases and check visitors.
The first troops are expected to arrive towards the end of March.
Lakenheath is a base for US F-15 aircraft, the headquarters of the third US air force is based in Mildenhall and Molesworth is a military intelligence centre.