The United Nations' former chief weapons inspector Hans Blix has said Iraq probably destroyed all of its weapons of mass destruction (WMDs) more than a decade ago.
Hans Blix spent several years searching for Iraq's weapons
In a telephone interview from his home in Sweden, Mr Blix told an Australian radio station the coalition may find documents relating to WMDs in Iraq, but not much else.
US President George W Bush and British Prime Minister Tony Blair referred to an imminent threat posed by Iraqi weapons of mass destruction as a prime justification for going to war in March.
But Mr Blix said the veil thrown up by the former Iraqi President Saddam Hussein over WMDs was probably meant to deter a military attack.
"If [Iraq] didn't have any [WMDs] after 1991, there must be some explanation why they behaved as they did. They certainly gave the impression that they were denying access [to weapons inspectors] and so forth," Mr Blix said.
"You can put up a sign on your door saying "Beware of the Dog" without having a dog," he added.
The US Government has consistently said the search for weapons of mass destruction in Iraq will take time and maintains it is confident it will uncover evidence of the threat they posed under Saddam Hussein's control.
But Mr Blix - who spent three years searching for Iraqi chemical, biological and ballistic missiles as head of the UN Monitoring Verification and Inspection Commission (Unmovic) - says there may be nothing there to find.
"The more time that has passed, the more I think it's unlikely that anything will be found," Blix said in the interview, broadcast on Wednesday.
"I'm certainly more and more to the conclusion that Iraq has, as they maintained, destroyed almost all of what they had in the summer of 1991," he said.
Mr Blix left Iraq with his team of weapons inspectors ahead of the March attack on Iraq.
The UN inspection team has since been replaced by the US replaced Iraq Survey Group, which is US-backed.
The group consists of about 1,500 weapons inspectors who have been looking for WMDs in Iraq for the past five months.
But they have so far failed to uncover any weapons of mass destruction in the country.