America stepped up its drive towards war last night, saying that Saddam Hussein was in "material breach" of United Nations resolution 1441. At the same time it announced that it was doubling its forces in the Gulf.

It gave its verdict on Iraq´s 12,000-page declaration on weapons of mass destruction after Hans Blix, the chief UN weapons inspector, told the Security Council that the document contained little new.

Mr Blix said it was based largely on statements Iraq made during inspections between 1991 and 1998, after which inspectors were forced to leave.

"There were a lot of open questions at the end of 1998. These have not been answered by evidence in the new declaration.

"The absence of that evidence means that we cannot have confidence that there are no remaining weapons of mass destruction. We will continue to look for that in the inspections process." Colin Powell, the American secretary of state, said the declaration represented a "material breach", adding that it "totally fails to meet the resolution´s requirements".

While stopping short of saying that this would be the final trigger for conflict, Washington´s formal response was designed to force the pace of preparations for war.

It also indicated that the days of the inspections were numbered.

A senior White House official said the verdict marked a turning point in policy towards the Iraqi dictator and signalled that President George W Bush was "ramping up" towards war.

John Negroponte, the American ambassador to the UN, said the declaration "clearly shows that Iraq has spurned its last opportunity to comply with its disarmament obligations".

He said: "It is truly unfortunate that Iraq has begun what was supposed to be a new chapter in compliance with council resolutions by falling back on the regime´s practice of omissions, evasions and untruths." Its declaration, presented nearly two weeks ago, appeared to be "one more act of deception in a history of lies from a defiant dictator".

Mr Negroponte said: "These are material omissions that, in our view, constitute another material breach."

He added that America had asked for more frequent briefings from the chief weapons inspector.

Mr Blix is due to give a definitive assessment of the declaration on Jan 27 - a Security Council meeting that could turn out to be the immediate precursor to war.

Jack Straw, the Foreign Secretary, said the declaration represented "a very serious failure to comply" and that "a clear warning has to go out to Iraq that they now have to co-operate fully with the UN and its inspectors".

Mr Straw said that war was not inevitable but, through the declaration, Iraq had pulled one "trigger".

He added: "They now, in a sense, have their finger on the other trigger."

America is alone in considering the declaration, which said that Iraq had no weapons of mass destruction, as a "material breach" in itself.

Britain, France, Russia and China, the four other permanent members of the Security Council, believe that Saddam has to impede the work of inspectors to fall foul of the resolution.

This distinction, however, is unlikely to make any difference to the final outcome because Washington and London are convinced that Saddam is certain to try to impede the inspectors in the coming weeks.

Those weeks will be used by America to put its forces in place and enlarge the number of allies providing both moral and practical support.

As Mr Blix was addressing the Security Council, Gen Tommy Franks, the military commander in the Gulf, was at the White House presenting Mr Bush with the latest Pentagon plans.

More than 50,000 ground troops are expected to be sent in addition to that number in place or on their way. Britain is to send up to 20,000 soldiers. This, with air force and navy personnel, will bring the total allied strength to around 130,000.

Some 15,000 American army and marine corps ground troops are in the region already, most of them in Kuwait.

Iraq remained defiant. "This is the interpretation of the United States and does not represent the interpretation of the whole international community," said Muhammed S Ali, its deputy ambassador to the UN. (© Copyright of Telegraph Group Limited 2002. 12/20/02)