Government officials say the prime ministers of Britain and Ireland, David Cameron and Enda Kenny, will travel to Belfast later this week in hopes of forging an agreement to sustain Northern Ireland's fraying unity government.

The planned arrival of both leaders Thursday signals increased concern that the 7½-year-old coalition of British Protestants and Irish Catholics, a key peacemaking achievement, could collapse without a new compromise pact.

The two principal parties in Northern Ireland's five-party coalition, the Irish nationalists of Sinn Fein and the British unionists of the Democratic Unionist Party, remain at loggerheads on a growing list of security, economic and cultural matters. The negotiations, which began in September, face an informal Christmas Eve deadline.

Failure to compromise could mean early elections or the renewal of direct British rule.