Belfast, Northern Ireland ? Northern Ireland faces a crossroads this week in its battle to sustain a 1998 peace accord that has fueled Catholic demands and Protestant fears almost to the breaking point.

In the most divided quarters of Belfast, this tension inspires chronic rioting and the construction of so-called “peace lines,” walls of brick and steel that scar the landscape.

Inside Northern Ireland’s administration of British Protestants and Irish Catholics, the heart of the Good Friday pact, more dangerous fault lines run.

First Minister David Trimble struggles daily with his many Protestant critics and sometimes, he concedes, his own conscience about leading his Ulster Unionist Party 2 1/2 years ago into a four-party coalition involving Sinn Fein, the public face of the secret Irish Republican Army.

The IRA’s surprise apology last week for killing civilians appeared timed to curry favor with British Prime Minister Tony Blair, who plans a major statement on the tensions between Trimble and Sinn Fein this week.

The Ulster Unionist chief, who accuses the IRA of repeatedly violating its 1997 cease-fire, says Blair must spell out a new policy on punishing Sinn Fein for IRA activities.

Sinn Fein leader Gerry Adams says Blair must favor his own shopping list, including amnesties for IRA fugitives.

The accusations against the IRA have mounted: Designing new weapons and training rebels in Colombia, stealing anti-terrorist intelligence documents, compiling dossiers on targets, shooting Protestants in Belfast riots.

The IRA denies it all, but the outlawed group never has renounced violence. And asked Saturday if the IRA campaign to demolish Northern Ireland as a British territory was over for good, Adams hedged his bets, saying, “None of us can take this for granted.”

Blair plans a Northern Ireland policy statement Wednesday, just before Parliament in London adjourns for the summer. Many province politicians already are on holiday.

The Ulster Unionists, badly divided since Trimble gambled on the Good Friday accord, return in September to select candidates for what looks like Northern Ireland’s most competitive and crucial election ever. They fear taking a historic beating unless Britain helps them get tough on Sinn Fein.

Whichever party wins the most seats next May to refill the 108-seat legislature claims Trimble’s post. Support for Ian Paisley’s deal-wrecking Democratic Unionists has surged since Sinn Fein gained some power.

The extremist parties participate in the power-sharing government, but they do not control. If Paisley defeats Trimble next year, he could knock the whole power-sharing house down.

Northern Ireland elected the power-sharing legislature in 1998.