"But Tony Blair's behaviour since September 11 has left Americans automatically assuming he will back any decision taken by US President George Bush," he added.

"The support of Britain is assumed. I think it would be shocking if Britain did not go along with the United States, whatever President Bush's decision might be," Gen Clark said.

"Prime minister Blair has been so incredibly supportive of the United States ...that I think it hasn't really penetrated popular understanding in the United States that there is some possibility that the UK wouldn't be there with us."

Gen Clark put the chances of a US-led military strike against Iraq next year at 65%-70%.

"It is likely, it is probable. It is not 100% absolute," he told BBC Radio 4's Today programme.

Mr Bush's talk of "an axis of evil" and his calls for "regime change" in Iraq had left him little room for manoeuvre, the general added.

"It is going to be very difficult if the covert action doesn't work. If an international consensus doesn't come together I think it is going to be very difficult for him to find another course of action," he said.

But he warned that war might not be the most effective way of dealing with Saddam Hussein.

"You can get a strategically decisive result without having to use strategically decisive and destructive military power if you bring in the elements of the international law and the full diplomatic weight of the international community," he said.

"If we were able to do that in Iraq we would have a much better result of not just in taking down Saddam Hussein's regime but in controlling proliferation of weapons of mass destruction, in preventing the inflammation of the Arab world and in dealing with the aftermath in Iraq."

Privately even the hawks within the US government lobbying for war acknowledged that President Saddam was no threat to America, according to the general.

And they had been arguing for the attack long before September 11, he said.

"There are some in the administration who have always felt that military power should be used to eliminate Saddam Hussein.

"Secondly, those who favour this attack now will tell you candidly, and privately, that it is probably true that Saddam Hussein is no threat to the United States.

"But they are afraid at some point he might decide if he had a nuclear weapon to use it against Israel."