The leaders of Britain and Ireland appealed Thursday to the Irish Republican Army to disarm and disband as part of a new diplomatic push to bring a stable Catholic-Protestant government to Northern Ireland.

"This is the moment of decision as to whether those acts of completion will happen or not," British Prime Minister Tony Blair said at the start of an expected three days of negotiations between political figures from Northern Ireland at a castle southeast of London.

Any agreements achieved at Leeds Castle will hinge on new peace commitments from the outlawed IRA, which is not officially at the table.

A cross-community administration for Northern Ireland, the central achievement of the U.S.-brokered Good Friday accord of 1998, fell apart two years ago, after a string of crises linked to the IRA's activities and refusal to disarm.

Blair and the Irish Prime Minister Bertie Ahern have long agreed that any revival of power-sharing requires the IRA to disarm and cease a specific list of activities, including breaking the limbs of criminal opponents and gathering intelligence on potential British targets. Both are gambling that negotiations with the IRA's affiliate political party, Sinn Fein, will achieve that goal.

Sinn Fein, which has become the major Catholic-backed party in Northern Ireland since the IRA cease-fire of 1997, accepts that its growth will require the IRA to keep fading into the background.

Party leader Gerry Adams, who many people suspect has been an IRA commander for the past three decades, emphasized as he arrived Thursday that he wants to reach a binding deal with Ian Paisley's Democratic Unionists, who represent most of the province's British Protestant majority.

President Bush's envoy for Northern Ireland matters, State Department official Mitchell Reiss, was also taking part in the Leeds Castle talks. The Bush administration has backed the joint British-Irish goals for the negotiations.

Sinn Fein wants any moves by the IRA to yield maximum concessions in return. At the top of the list: Any new administration must have control of the police and justice system. Britain retained those responsibilities in the previous power-sharing experiment.

Adams also highlighted another Sinn Fein complaint: continued surveillance and wiretapping by British spy agencies. He displayed an electronic bug that was discovered inside Sinn Fein's Belfast headquarters. "We think it's the height of hypocrisy and bad faith," he said.