By Steve Schifferes BBC News Online Washington correspondent

The Bush administration continued its drive for support on its Iraq policy by sending senior State Department officials to Capitol Hill to explain the case against Saddam Hussein.

But influential senators have asked for Secretary of State Colin Powell himself to appear before Congress before he reports to the United Nations on 5 February to explain what new evidence there is to link Saddam Hussein with terrorism.

I think the American people are feeling, with the inspectors in there, there is a sense of security Republican Senator Lincoln Chafee

Others expressed scepticism that Iraq presented a imminent danger that justified war, at least while the inspectors were present.

The questioning came as the Senate Foreign Relations Committee heard testimony from US Ambassador to the UN John Negroponte and Deputy Secretary of State Richard Armitage on the US response to the report to the UN by Hans Blix.

Widespread support

Mr Armitage said that it was clear from the chief arms inspector's report that "substantive co-operation was sorely lacking."

Some senators want to give inspectors more time

The top officials said that they were beginning a period of "intensive diplomacy" to gain the support of the rest of the UN Security Council for a second resolution authorising the use of force against Iraq - which they called "desirable but not necessary", following the appearance next week of Mr Powell.

And Mr Armitage said that the US had received widespread pledges of military support in the case of war, including nine countries which had offered troops and 20 which would allow US basing rights or overflights - although he declined to name the countries in public.

Ranking Democratic Senator Joe Biden, who says he supports the war resolution, expressed worry that - without further evidence - leaders of other countries would feel unable to join the US effort.

He said that so far the US Government "was confusing the devil out of the world".

And he stressed that it was important that, if war came, the US had widespread international support.

Several senators said that the inspectors should be given more time to do their work.

Republican Senator Lincoln Chafee said: "I think the American people are feeling, with the inspectors in there, there is a sense of security."

Links to terrorism

Senator Russ Feingold questioned whether there was any evidence that Iraq had transferred weapons of mass destruction to terrorists or other states, or had engaged in more proliferation than countries like North Korea or Iran.

Senator Lugar chaired the hearings

Assistant Secretary of State for non-proliferation John Wolf told the senators that Iraq was a buyer of weapons of mass destruction - not a seller - but that it was a threat to the region and its own people.

And Mr Armitage indicated that Secretary Powell would present more evidence to the UN about the way Iraq was harbouring terrorists - although so far the only publicly identified group is based in northern Iraq, an area not under the control of the Saddam Hussein regime.

Democrat Senator Barbara Boxer indicated her desire to let the inspectors have more time to work, and pointed out that the US had provided the weapons of mass destruction to Iraq in the first place, during the Iraq-Iran war.

New Senate resolution

Senior senators on the committee indicated that they were unhappy with the Bush administration's unilateral approach to other international matters, such as the Kyoto Treaty and the international criminal court, which they said made it more difficult to get support now.

Senator Christopher Dodd said that the American people needed to hear the evidence against Iraq before the UN, and asked for Mr Powell to appear before the full Senate next week to present his case.

But even on the Democratic side, there seemed to be little support on the foreign relations committee for a new congressional resolution authorising war against Iraq - as suggested on Wednesday by Democrats Edward Kennedy and Robert Byrd.

Such a proposal would have to come before the committee before reaching the floor of the Senate.

However, the surprising mood of scepticism evident in the committee room was an indication that President Bush and Mr Powell still have work to do if they are to gain bipartisan support for their Iraq policy.