Guerrillas fighting British rule in Northern Ireland declared a three-day Christmas truce, and Britain said it hoped the cease-fire would help lead to the solution of a conflict in which 3,000 have died in 21 years.

Northern Ireland Secretary Peter Brooke said the truce that started at midnight Sunday "albeit brief, is a welcome epitaph to 1990 and may be a pointer to achieving a lasting solution in 1991."The Irish Republican Army has regularly held informal Christmas cease-fires, but the last to be announced in a statement - as this one was - was back in 1974.

That cease-fire was extended well beyond Christmas, ending only after eight months of fruitless efforts to get peace talks off the ground.

Irish Prime Minister Charles Haughey said the new cease-fire, if extended, would "open up great possibilities for progress."

James Molyneaux, leader of Northern Ireland's Official Unionist Party, which strongly supports continued ties with Britain, denounced the IRA move.

"Criminals deserve no medals for ceasing criminal activity for three days," he said. "It will be small comfort for families of policemen and soldiers to know that their loved ones will not be murdered until Thursday."

The IRA has recently been using "human bombs" - strapping people into vehicles laden with explosives and forcing them to drive to security checkpoints.

One such attack in November killed seven people, including six British soldiers. The total death toll this year is 74.

Sunday's IRA statement, released in Belfast, said its active service units had been told "to suspend all offensive military action in the British-occupied area for a period of three days from midnight tonight until midnight on Dec. 26."

But the IRA stressed that its units would fight back in self-defense if attacked during the period.

Brooke has made several appeals for the IRA to end its campaign and a year ago indicated the government could respond "imaginatively" if the shooting and bombing stopped.

Irish political analysts said a peace initiative by Brooke would enter a critical phase in coming weeks.

It was at least possible that Sinn Fein, the political wing of the republican movement, might favor an indefinite IRA truce that could enable Sinn Fein to participate in talks.

Britain three weeks ago flew an extra battalion to Northern Ireland, bringing the number of its troops there to 11,000.

Security sources say British reinforcements and stepped-up patrolling averted a pre-Christmas IRA offensive.