Government sources say the resignation of Mr Peter Mandelson will not disrupt the intensive efforts to reach agreement in the Northern talks.
As senior Government officials held talks in Belfast with the pro-agreement parties yesterday, Government sources said they believed Mr Mandelson's resignation at this crucial stage would have a minimal effect. The British Prime Minister, Mr Tony Blair, and his chief of staff, Mr Jonathan Powell, had taken a central role in the past 10 days, the sources said, and this would continue.
There was "very serious engagement" taking place on the issues of decommissioning, scaling down the British military presence in nationalist areas and policing, they said. Talks are expected to continue until the end of next week, with the Taoiseach, Mr Ahern, travelling to London to meet Mr Blair.
As the Taoiseach, the Minister for Foreign Affairs and opposition spokesmen paid tribute to Mr Mandelson yesterday, the Government expected an early replacement of the Secretary of State for Northern Ireland.
Mr Ahern said he regretted "that circumstances have arisen which have led to the resignation of the Secretary of State for Northern Ireland, Mr Peter Mandelson MP. I applaud the role he has played in the ongoing inclusive implementation of the Good Friday agreement."
The Minister for Foreign Affairs, Mr Cowen, said yesterday he was sorry to hear of Mr Mandelson's resignation and paid tribute to his personal contribution to the peace process. Although Mr Cowen and Mr Mandelson did not have a personally warm relationship, sources said they worked well together. Mr Cowen said that as Mr Mandelson left office, the difficult issues were being confronted.
"Peter will rightly be remembered for the important role he has played in enabling us to come so far - including in achieving the establishment of the institutions in December 1999. "I pay tribute to his significant personal contribution to the peace process, and offer him my best wishes for the future."
The Labour Party leader Mr Ruairi Quinn described Mr Mandelson's resignation as "a significant blow to the prospects for political progress in Northern Ireland, coming as it does at a time when the talks between the two governments and the Northern parties are poised at such a delicate point."
He said the Irish people owed Mr Mandelson "a considerable debt of gratitude for the Trojan work he put in during his period in office, often in the face of hostile media and political comment."
Fine Gael's Northern Ireland spokesman, Mr Brian Hayes, said he was disappointed at the resignation. Mr Mandelson had made an important contribution to the peace process, he said.