US Defence Secretary Donald Rumsfeld has told the BBC he believes Iraq is capable of building new weapons even with inspectors in the country.
Donald Rumsfeld said military action could still be averted
Mr Rumsfeld said he had "no doubt" that Iraq had chemical and biological weapons, and that it had been working on nuclear weapons.
In an exclusive interview broadcast on Tuesday, he said even the destruction of al-Samoud missiles II as demanded by the United Nations was no real sign of disarmament.
Mr Rumsfeld - seen as one of the leading hawks of the Bush administration - told the BBC's David Dimbleby he was not impressed by Saddam Hussein's level of co-operation with the United Nations weapons inspectors.
"Every single thing that he does, that anyone could cite is co-operative, was after some long period of denying, of refusal to do it, and ultimately a willingness to do part of it," Mr Rumsfeld said.
"I think the way to think about that is that there were inspectors there before, and he continued with his weapons of mass destruction programmes.
"And the way he did it is he's learned how to live in a, so to speak, in an inspections environment.
"He does things underground. He's very skilful at denial and deception."
Mr Rumsfeld said he still hoped war could be avoided - either by Saddam Hussein co-operating with the United Nations, the Iraqi leader going into exile, or if there was a coup against him.
The US and UK is trying to get support from the UN Security Council for a second resolution authorising the use of force against Iraq. But France and Russia are strongly opposed to military action and have both warned they might - as permanent members of the Security Council - veto any resolution.
Mr Rumsfeld said the US understood that "these are tough issues, and people can differ on them" - saying the US had been prepared to give the Security Council members "more time".
But he warned that time was running out.
"It's been months. It's been months since the United States took this issue to the United Nations," he said. "If you think back, the United Nations has had this for 11 years, 12 years."
Mr Rumsfeld said Iraq was a threat to the world, as well as to US interests.
"The issue that's before the world, it seems to me, is the pervasiveness of weapons of mass destruction and the spread of these, the proliferation of these technologies, chemical and biological weapons, increasingly nuclear weapons.
"We could in 10 years have double the number of nuclear powers in the world.
"The situation with Iraq is that we're at the end of the string. We've tried diplomacy for 12 years. We've tried economic sanctions, and they have not worked."