Northern Ireland's political rivals signaled today they were determined to break the past year's stalemate, making conciliatory statements and building expectations of an important Irish Republican Army (IRA) announcement.

In a pivotal concession, Ulster Unionist leader David Trimble dropped his Protestant party's refusal to form a Protestant-Catholic administration for Northern Ireland--the intended cornerstone of the Good Friday peace accord of 1998--in advance of receiving an IRA promise to disarm.

The IRA-linked Sinn Fein party, which is to receive two posts within the proposed 12-member cabinet, in exchange called disarmament "an essential part of the peace process."

The emerging compromise, mediated by former U.S. senator George Mitchell during the past 11 weeks, depends upon the IRA appointing a senior figure to negotiate terms with a disarmament commission. Politicians expect the group's ruling Army Council to confirm this decision in a policy statement by Thursday.

Trimble, who had sought a fixed date for disarmament to start, indicated today he would now recognize this gesture as providing a "genuine and meaningful" measure of the IRA's commitment to destroy its weapons stockpile.

Ulster Unionist negotiators, speaking on condition of anonymity, say a key factor was an assurance that the IRA representative would be the group's alleged senior commander, Brian Keenan. Keenan, 57, has served 14 years in prison for IRA activities. He speaks French, Arabic and German--and British and Irish police say he opened arms-supply channels with Libya and organized bombings in England in the 1970s. He has spoken out at IRA rallies against the notion of decommissioning weapons.

But both sides must try to minimize damaging splits in the coming weeks to keep compromise in the cards.

Until now the IRA has rejected the accord's expectation of total disarmament by May 2000 and refused to appoint a representative to the disarmament commission, which is led by Canadian Gen. John de Chastelain. This step is considered a bridge too far for some IRA activists, and could encourage defections to dissident groups.

Trimble's shift triggered immediate criticism from hard-line Protestants, including rebels within his own party, who still must vote on the policy change. Trimble could be ousted as Ulster Unionist leader if he loses the vote, which is expected in about two weeks.

In their complementary statements, the Ulster Unionists and Sinn Fein seemed determined to send sympathetic signals to each other in defiance of their own hard-liners.

They offered near-identical evocations of a future Northern Ireland where British Protestants and Irish Catholics work together.

"Both of our traditions have suffered as a result of our conflict and division. This is a matter of deep regret, and makes it all the more important that we now put the past behind us," Trimble said on the steps of the negotiating venue.

"All sections of our people have suffered profoundly in this conflict. That suffering is a matter of deep regret but makes the difficult process of removing conflict all the more imperative," said the Sinn Fein statement, issued in the name of party leader Gerry Adams. "Sinn Fein wishes to work with, not against, the unionists and recognizes this as yet another imperative."