Northern Ireland Secretary Peter Hain postponed a meeting set for Tuesday between the Protestant Democratic Unionist Party (DUP), led by Ian Paisley, and the Catholic Sinn Fein, headed by Gerry Adams.
Under a plan agreed by the Irish and British governments last week in St Andrews, Scotland, a so-called Programme for Government Committee was to start meeting regularly to begin preparing for a resumption of self-rule.
The postponement followed a dispute over whether Sinn Fein's Martin McGuinness, a former IRA commander, would swear an oath to support the police and rule of law.
"It has become clear to me this morning that there are differences in the understanding of parties of what the St Andrews Agreement will mean for the pledge of office," Hain said. "It is important that this is resolved quickly."
The St Andrew's Agreement still has to be formally endorsed within the next month by parties in the currently British-run province before a power-sharing government can be restored, four years after it was suspended.
Under the plan set out by Prime Ministers Tony Blair of Britain and Bertie Ahern of Ireland, government could begin operating again from Belfast's Stormont Castle from next March.
Blair and Ahern were key contributors to hammering out the landmark 1998 Good Friday agreement, ending some three decades of so-called Troubles which left over 3,500 people dead, many at the hands of the IRA.
But self-rule was suspended in 2002 following allegations of an IRA spy ring operating at Stormont, and the province has been under direct rule from London ever since.
"It appears unlikely that we will take part in the meeting at leadership level," said Paisley's son, also called Ian, a leading DUP member.
"In St Andrews, we'd agreed that Sinn Fein would need to take a pledge of office before the moment of designation (on November 24th)," he said. "Sinn Fein seems to have difficulties with this now."
On November 24 the Belfast assembly is to meet to nominate a first minister and deputy first minister -- although they will not immediately hold power. That will only happen on March 26 next year, after the Northern Irish electorate have been asked to vote, either in a referendum or an election.
A spokesman for Sinn Fein said: "This issue was not raised in St Andrews last week, certainly not the issue of policing and law and order in respect to the pledge of office."

Copyright AFP (Agence France-Presse), 2006