The foreign secretary has said that the United Nations may not vote on a new resolution on Iraq.

But the British government remains "hopeful" that the security council will reach a conclusion before the end of this week.

In a briefing to journalists on Wednesday, Jack Straw said the British government was discussing six tests to measure Iraqi progress on disarmament.

But he declined to guarantee that the compromise resolution will eventually be put to a vote of security council members.

"Let us see whether we get there," said Straw .

His statement came shortly after the Spanish government indicated that a failed resolution could undermine the case for military action.

As the diplomatic endgame proceeded in New York, the foreign secretary also repeatedly criticised the French pledge to veto any resolution regardless of the circumstances.

Straw said that each test was "demanding but eminently deliverable".

The UK is demanding a televised admission, in Arabic, by Saddam Hussein that he has concealed weapons of mass destruction.

At least 30 scientists should be allowed to attend interviews outside Iraq and more evidence on Iraqi anthrax stockpiles and unmanned aerial vehicles should be provided.

Banned missiles must be destroyed while mobile biological warfare production units should also be surrendered to weapons inspectors, the tests will say.

"These tests are not traps," said Straw. He added that they had been drawn from information set out by Hans Blix.

"Each one of these tests could be met promptly if only Saddam Hussein were to make the strategic choice to cooperate with the United Nations.

"And we are not asking that Saddam disarms completely within the timescale anticipated, we have never done so.

"What we are however asking, is that these tests are used as a measure of whether at long last he has come into cooperation."

But he reaffirmed that the March 17 deadline for Iraqi compliance could only be moved by "a matter of days but not in terms of weeks or months".

The foreign secretary said the UK would continue to back a second resolution despite French pledges to veto any move to authorise military action.

"What I guarantee is that we are working as hard as we possibly can to secure a second resolution.

"We are having to do so in circumstances in which one of the permanent members have said that whatever the circumstances they will veto the resolution, so that is not easy."

He added that the French position on use of the veto was "a very broad statement" but said that he was "hopeful" that the security council resolution would be passed.