President calls for support inside and outside America

President George Bush kicked off in earnest his efforts to win domestic and foreign support for an attack on Iraq yesterday, promising to seek congressional approval of any such move, and warning the world that "its credibility is at stake" over the issue of removing Saddam Hussein from power.

"Today the process starts," Mr Bush said after he met Republican and Democratic congressional leaders at the White House – his first important engagement since his month-long holiday in Texas – which focused on the gathering likelihood of an American-led assault on Iraq.

His remarks came amid growing signs that Mr Bush, like Tony Blair, who will make a flying visit to Camp David this weekend, is preparing to make public evidence of President Saddam's build-up of weapons of mass destruction, which sceptics of military intervention demand as a minimum condition before Mr Bush acts.

Shortly after the President spoke, one of the administration's most vocal hawks on Iraq, the Defence Secretary, Donald Rumsfeld, went to Capitol Hill to give a closed-door briefing to key senators and congressmen, including an "operational update" on the war on terrorism.

Mr Rumsfeld, who believes America should act even without international support, may present the intelligence information at which he has hinted, suggesting President Saddam is close to developing nuclear weapons he could make available to terrorist groups. It was already publicly known that Iraq wanted to acquire nuclear weapons, that nuclear technologies had spread in recent years and that Iraq had ways of obtaining such materials, Mr Rumsfeld asserted at a Pentagon briefing this week.

Such evidence will help to win over Congress, ever jealous of its constitutional prerogative to declare wars, however often that prerogative has been ignored in the past – and even though the White House lawyers have concluded that Mr Bush has sufficient authority under existing congressional resolutions to proceed militarily against President Saddam. Though most politicians of both parties favour the ousting of President Saddam, many say that Mr Bush has yet to make the case in sufficient detail. The Senate would find it "very hard" to pass a resolution without more information and evidence of international support, Tom Daschle, the Democratic majority leader warned. But, added John McCain, the Arizona Republican who gave Mr Bush a tough fight in the 2000 primary campaign, "once that happens, I'm sure both Houses will support the President."

But everything Mr Bush said yesterday strengthened the impression given by the bellicose language of Vice-President Dick Cheney last week, that he has broadly made up his mind to remove President Saddam by force, even though White House spokesmen insist for the record that no decision has yet been taken.

"This is a man who said he would not arm up, and that he would not harbour weapons of mass destruction," Mr Bush declared. But "for 11 long years, Saddam Hussein has sidestepped, craw-fished, wheedled out of any agreements he had made. So I'm going to call upon the world to recognise that he is stiffing the world," the President said.

The world had to realise its credibility was at stake. Saddam Hussein was "a significant problem and a serious threat, and something this country must deal with".

Colin Powell, the Secretary of State and presumed to be the leader of the moderate faction within the administration, also indicated that Mr Bush was nearing a final decision. The Iraqi leader had been "conning" the world about his weapons programmes, said General Powell, a leading proponent of securing United Nations approval before an attack.

He has been backed by the former president Bill Clinton, who ordered Operation Desert Fox, the last big air offensive against Iraq, after the eviction of UN weapons inspectors in December 1998. Mr Clinton warned that if President Saddam did possess chemical and biological weapons – "and I believe he does" – then he would have no incentive not to use them in the event of an attack. "The question is how Saddam should go, the circumstances in which he goes, not whether he should go ... I think we should give the inspection team one more shot," Mr Clinton said.

Once the charges against President Saddam are set out, Mr Bush could seek broad congressional endorsement for military action before it goes into recess in October in preparation for mid-term elections a month later.