Chief United Nations Weapons Inspector Hans Blix has expressed doubt over whether Iraq possesses weapons of mass destruction.

"The $64 billion question -- that's what the war is costing at the moment, I'm told -- is: are there any weapons of mass destruction?" Blix, Executive Chairman of the UN Monitoring, Verification and Inspection Commission, told UN Radio in an interview on Wednesday.

Blix and his team of inspectors left Iraq just before the US-led invasion began.

His report to the UN Security Council earlier that no WMDs had been found in Iraq was greeted with scepticism by the US and Britain.

In the interview, Blix pointed out that almost two weeks into the war, no WMDs have been found. But he added that the US-led coalition has an advantage in looking for banned weapons.

"There is one factor that makes it less difficult for the US to find them… and that is that as the country becomes liberated from the secret police, people may not fear speaking," he said.

UN inspectors had tried to interview Iraqi scientists and other personnel on the weapons. The Iraqis were afraid that "if they displeased the authorities they would be in trouble", Blix said.

"Now if they don't feel that there's such risk, then they might speak more freely.

"That might lead them, the Americans and British, to any secret storages, if there are any," he added.

Asked which WMDs he feared most, Blix said, "I'd think that in terms of military use, probably mustard gas and sarin… these are the things that they used in the war with Iran.

"The VX is also a horrible nerve agent."

But Blix said he did not believe Iraq would use such weapons even if it had them.

"My speculation is that since Iraq has denied having these weapons, if they were to use them, then the whole world would say, 'Well, they were liars.' Then many would also consider that the war is justified," he said.

Blix plans to leave his UN post in June when his contract expires.