Round-table talks between the Democratic Unionist Party (DUP) and Sinn Fein have been called off after a dispute over policing.
DUP leader Ian Paisley refused to attend today's historic face-to-face discussion with Sinn Fein counterpart Gerry Adams, in the first sign of cracks in last Friday's St Andrews agreement.
Under the Scottish deal, Northern Ireland politicians were given until November 10th to agree to a timetable set out by the British and Irish governments on restoring power-sharing government to the Stormont assembly.
A first minister and deputy first minister were then due to be nominated on November 24th, but there appears to be confusion about the pledge of office that all politicians taking part in power-sharing will have to sign.
Mr Paisley, who as leader of Northern Ireland's largest party will be nominated as first minister, believed Sinn Fein chief negotiator Martin McGuinness, who is likely to be his deputy, would have to sign up to the pledge on November 24th.
This would commit him to support for the Police Service of Northern Ireland (PSNI) and the rule of law. However, Sinn Fein do not want to do this until after their party holds a special conference on policing - which will happen after the November 24th deadline.
As a result, Mr Paisley this morning refused to attend the programme for government committee, and his son, Ian Jnr, said: "We need to talk with the government about these matters before he starts going to programme for government meetings."
In a statement, Northern Ireland secretary Peter Hain said: "It has become clear to me this morning that there are differences in the understanding of parties in what the St Andrews agreement will mean for the pledge of office."
He stressed: "It is important that this is resolved quickly." Mr Hain has now called on a separate committee to discuss the question of the oath of office "urgently".
Commenting this morning, SDLP leader Mark Durkan - a republican - urged the unionists to reconsider their call for the pledge of office to be signed by November 24th.
"The DUP's own process of consultation will continue long after that date. They will be saying that they will not be going into office "unless and until delivery". How can they say that if there has already been a full-blown pledge of office?" he said.