"
It could be that one day [the US] will say, 'Move aside boys, now we are coming in'... but I think a great many people and a great many governments would prefer to have disarmament through peaceful means.
"
Hans Blix
But Hans Blix, the head of the United Nations team, told the BBC he could not be certain he would be given enough time to declare Iraq clear of weapons of mass destruction - and thereby avert war.
"There is a certain momentum in the [military] build-up and that worries a great many people including myself," he said.
"Yet I have to listen to what the president of the United States says, namely that the use of force is only the method of last resort."
US President George W Bush and UK Prime Minister Tony Blair indicated on Monday they had no set timetable for war.
Both countries have been increasing their military presence in the Gulf.
Mr Bush said the US and its allies will disarm Iraq by force if it fails to comply with the UN teams searching for evidence of weapons of mass destruction.
Last month Mr Blix complained of a lack of support for the inspectors from the US and UK who, he said, were not sharing their best intelligence.
Some of that information has now been made available, he said, and as a result new sites had been inspected.
"I felt in the past that they were a bit like librarians who had books they didn't want to lend to the customer, but I think that's changing," he told the BBC.
Mr Blix said inspectors had found Iraq had imported weapons material in violation of UN rules.
But they had not yet determined if that was related to weapons of mass destruction such as nuclear bombs or chemical warfare.
He cautioned that it would be impossible to give a full guarantee that Iraq had no banned weapons and that political leaders would have to decide whether any assurance he could give were sufficient.
The military build-up added another dimension.
"It could be that one day they will say, "Move aside boys, now we are coming in - that's possible - but I think a great many people and a great many governments would prefer to have disarmament through peaceful means," he said.
Mr Blix's colleague, Mohamed ElBaradei, has warned that inspectors still need "a few months" for their work.
No 'exact timetable'
KEY DATES
A spokesman for the US president said on Monday that Mr Bush thought it important that the inspectors had time to do their jobs.
"The president has not put an exact timetable on [action]," he said.
Mr Blix will make a key further report to the UN Security Council on 27 January and some have said that could be used as a deadline.
But while the US and UK continue their military build-up, defence chiefs insist they have no start date for war.
A BBC correspondent says the deployments could simply give the US more options - by being ready to launch a war before the punishing heat of the Iraq summer but not being committed to it.
Britain's Tony Blair said he would expect members of the UN to act if Iraq was shown to be continuing to ignore UN demands.
He said he had "no doubt" that Saddam Hussein was attempting to rebuild his alleged nuclear, biological and chemical weapons arsenal.
But he said he did not want to impose an "arbitrary timescale" on if and when action should be taken.