Tony Blair insisted yesterday that Saddam Hussein was "rattled" - and confidently predicted the British public would back military action against Iraq if he failed to surrender his weapons of mass destruction.

The Prime Minister refused to rule out the use of non-conventional weapons, such as nuclear bombs or missiles, if Saddam used chemical or nerve agents against a coalition force.

Mr Blair said the Iraqi regime itself was weakening and that its days of playing "hide and seek" with UN inspectors were over.

He repeated his belief that there was no way out for Saddam other than disarming himself of weapons of mass destruction.

And he underlined the Government's message that it was inevitable that al Qaida-inspired terrorists would try to strike at the UK.

The premier's hardline comments came during a marathon session of evidence to the House of Commons Liaison Committee.

Under questioning by some of the most senior MPs in the Commons, Mr Blair repeated his determination to use the twin-track approach of diplomatic pressure through the United Nations backed by the credible threat of military force.

When Mr Blair was asked how the allies might react if Saddam appeared set to use his own weapons of mass destruction when faced with a military strike, he replied: "We are aware of the potential of that threat and we would deal with it in any way that we thought necessary.

"But I don't think it is wise for me to get into speculating as to exactly what we are doing about it."

Mr Blair said he appreciated current public concern but predicted support would swing behind any action if it was taken. "I understand what the difficulties of public opinion are and it's my job to explain to people why it's necessary. It's also the case that we are not in conflict yet.

"When and if that time came, people would find the reasons acceptable because there is no other route available to us."

The Prime Minister claimed the inspection regime now under way was beginning to take its toll on Baghdad, although Saddam boasted yesterday that he was not losing any sleep over the war machine gearing up around him.

But Mr Blair told MPs: "There is no doubt at all that as a result of the pressure, the regime in Iraq and Saddam's immediate entourage are weakening. They are rattled about the build-up of forces," he said.

The Prime Minister repeated it was "highly desirable" for a second United Nations resolution to back military action if needed but went on: "Of course it's better if we can go down the UN route, but we must not give a signal to Saddam that there's a way out of this."

Last night, President George Bush delivered similar warnings, saying it was now clear Saddam was not disarming. "It appears to be a re-run of a bad movie," he said. "He is delaying. He is deceiving. He is asking for time."

* A gunman attacked a Toyota off-roader during an ambush in Kuwait yesterday, killing one US civilian and critically wounding another.

It is the third shooting of Americans since October in the oil-rich emirate, where thousands of US troops are assembling for a possible strike on Iraq