The peace process appeared to be careering towards another crisis this week, with Sinn Fein threatening to collapse the power-sharing Executive if policing and justice powers are not devolved to Stormont.

Last weekend Sinn Fein's Caoimhghin O'Caolain warned that Republicans' patience over the failure to transfer policing was fast running out.

Policing and justice powers had initially been due to be transferred to the Stormont Executive in May, but that move was blocked by the Democratic Unionist Party (DUP), which claimed that Republicans needed to do more to instill confidence within unionism.

In June Sinn Fein threatened to block the election of Peter Robinson as first minister in protest at the continued delay. That threat was only averted by the personal intervention of British Prime Minister Gordon Brown.

Sinn Fein and the DUP then committed themselves to increased negotiations, with Republicans insisting that policing powers must be successfully transferred by the autumn.

However, with no sign of any imminent breakthrough, O'Caolain warned, "When Sinn Fein changed our policy on policing in the North, accepting that a new beginning was being made, it was with the prospect that policing and justice powers would be transferred by May of this year.

"It is now the end of August and we do not even have a date for transfer. This is totally unacceptable. Our negotiators are doing their utmost.

"But the DUP, the British government and the Irish government should note that the patience of Republicans should not be taken for granted.

"Our ministers are not in the Executive to fill seats, to make careers or to be administrators. Their mandate is to bring about lasting and fundamental change. That is why Sinn Fein put them there.

"If we are forced to conclude that change will not be forthcoming from the Executive then we will have no option but to pull out our ministers and seek to put pressure where responsibility ultimately lies, which is on the British government in London."

DUP leader Robinson warned his party would not bow to Sinn Fein threats. "Let me make it clear the DUP will not respond to threats such as that which Sinn Fein has made," he said.

"If we were to do so on this issue we would be vulnerable to having the Republican threat of bringing the institutions down used again and again in order that we would comply with other Sinn Fein demands.

"Nor indeed will we make political concessions in order to encourage any party to do that which it pledged to do and carry out duties which it is legally required to perform."

The Executive has not met since June due to the strains between Sinn Fein and the DUP. A date of September 18 has been set to reconvene, but Republicans have yet to indicate if they will take part.

Robinson said that there would be consequences for the North if the meeting does not go ahead as scheduled.