The United Nations' top two weapons experts have criticised the United States, saying that the invasion of Iraq was not justified by the evidence in hand.

"I think it's clear that in March, when the invasion took place, the evidence that had been brought forward was rapidly falling apart," Hans Blix, who oversaw the investigation into whether Iraq had chemical and biological weapons, told CNN on Sunday.

The evidence Secretary of State Colin Powell presented to the UN Security Council in February 2003 was "shaky", he said, adding that he told this to US officials, including National Security Adviser Condoleezza Rice.

"I think they chose to ignore us," Blix said.

Mohamed ElBaradei, Director General, the International Atomic Energy Agency, told CNN from IAEA headquarters in Vienna, Austria, that he had been "pretty convinced" that Iraq had not resumed its nuclear weapons program.

Days before the war began, Vice-President Dick Cheney had said, "We believe [Iraqi leader Saddam Hussein] has, in fact, reconstituted nuclear weapons. I think Mr ElBaradei, frankly, is wrong."

ElBaradei told CNN: "I haven't seen anything on the ground at that time that supported Mr Cheney's conclusion or statement…"

The Bush administration tended "to say that anything that was unaccounted for existed, whether it was sarin or mustard gas or anthrax," Blix said.

Blix also criticised Powell, who told the Security Council about an Iraqi site that held chemical weapons and decontamination trucks.

"Our inspectors had been there, and they had taken a lot of samples, and there was no trace of any chemicals or biological things," Blix said. "And the trucks that we had seen were water trucks."