A last minute intervention by the US government to help save the faltering Northern Ireland peace process has not been ruled out by Foreign Secretary, Robin Cook.

Speaking in Washington, Mr Cook said he discussed Northern Ireland at length with White House National Security Adviser Sandy Berger on Wednesday.

The meeting comes as a bill to re-impose direct rule in Northern Ireland received its Royal Assent at Westminster.

The legislation gives power to Northern Ireland secretary Peter Mandelson to suspend the nine-week-old power-sharing executive if the main republican paramilitary group, the IRA, fails to begin disarming by the weekend.

Speaking with reporters in the US capital, Mr Cook did not rule out a mediation role by the American government.

He said: "If it can assist in persuading the IRA to make such an offer, that would be very welcome."

The Foreign Secretary said the U.S., British and Irish governments, which co-sponsored the Good Friday Agreement, were united on two key points.

They believed suspension should only happen in extreme circumstances

The only way to avert the re-imposition of direct rule was for the IRA to come forward with what he described as "a credible commitment to disband and decommission".

He was at pains to point out that Britain did not want to stop the work of institutions it had sweated for months to create.

"I don't think there is any serious commentator or anybody who has followed this anything other than cursorily who can for one moment imagine it is a clever British plot to reimpose direct rule," he said.

"If we are to avert suspension, then some time over the next 24 hours the IRA have to come forward with a clear commitment that demonstrates their good faith and commitment to ending the armed struggle, and ending its capacity to carry out the armed struggle.

"We are very willing to hear from them how and when they intend to achieve that," he added.

Ulster Unionists are gathering on Saturday to review the progress on the arms issue since the executive was formed.

Party leader and First Minister David Trimble and the three Ulster Unionist ministers have threatened to resign in the absence of a weapons move by the IRA.