The decision affects both staff from Unscom, the United Nations commission monitoring weapons of mass destruction in Iraq, and UN humanitarian workers.

The withdrawal was ordered by UN headquarters in New York following discussions with US Government officials.

Richard Downes: Withdrawal came as a surprise

It follows an earlier ban by Baghdad on weapons inspections by Unscom staff.

Over 100 UN workers have left Baghdad travelling in convoy.

Military moves

On Wednesday the US Government was reported to have ordered a second aircraft carrier, the USS Enterprise, to speed up its approach to the Gulf.

USS Enterprise: Due in the Gulf 23 November

An "Air Expeditionary Force" of as many as 50 attack and support aircraft as well as radar-avoiding F-117A stealth fighters is also preparing to head for the region.

They will join an already substantial military force ready to launch an attack should President Clinton give the order.

"If we do something, it's not going to be a pinprick," one Pentagon official is quoted as saying.

Safety concerns

Richard Downes: US thought to be deploying new forces

UN spokesman Eric Falt said the decision to relocate non-essential staff to Amman in Jordan temporarily was "precautionary in nature, and is being instituted solely with the safety of UN staff in mind."

The decision also affects staff running the oil-for-food programme, under which Iraq is allowed limited exemption from trade sanctions to buy essential supplies.

Only a few UN staff will remain in Iraq, including the UN Secretary-General's personal envoy in Baghdad, Prakash Shah.

Although some Unscom staff began leaving Iraq at the weekend, the large-scale withdrawal of UN personnel has come as a surprise.

The BBC Correspondent in Baghdad, Richard Downes, says the withdrawal has increased speculation that the US may be about to use military force against Iraq.

Support for action

It would however be difficult for the US to act unilaterally. At present only the United Kingdom supports the US on the use of military force without a further UN resolution being passed.

In a statement on Wednesday the Iraqi government denied it had expelled the UN workers.

The authorities in Baghdad have also recently dismissed the possibility of an attack by the US and its allies.

Ealier, the United States warned that Iraq will be able to rebuild its weapons programme in a matter of months unless the international community takes action over its obstruction of UN weapons inspections.