Mr Hans Blix, the chief UN weapons inspector for Iraq, urged the US-led coalition to allow his team back into the country, saying it would increase the credibility of any weapons discoveries.
"I think the world would like to have a credible report on the absence or the eradication of the programme of weapons of mass destruction," he told the BBC in an interview at UN headquarters.
But the White House said it was not yet time to discuss the possible return of the inspectors, who were withdrawn from Iraq one month ago on the eve of the US-led invasion.
"At some point, UN inspections will be an issue that needs to be addressed, but at this point, the US and coalition forces are still engaged in actions," spokeswoman Ms Claire Buchan told reporters.
So far, the US and Britain have not found any chemical, biological or nuclear weapons in Iraq, although they control almost the entire country.
Mr Blix said it was "too early to draw conclusions," but added that he was "a little more inclined" than before to believe the insistence of the now defunct Iraqi government that it no longer had any such weapons.
Mr Blix said the weapons inspectors could be back in Iraq within two weeks of a green light from the Security Council
The UN weapons inspection team left Iraq just before the war after several months of inspections.
Agencies