A meeting to be held between the Irish and British prime ministers is the most crucial one the peace process has seen in 20 years, it has been claimed.

Sinn Fein's Martin McGuinness also said the next six to eight weeks of talks were the most critical in the last 100 years of Ireland's history.

The meeting between the prime ministers is due to take place in London on Thursday.

Gerry Adams: Met Irish prime minister in Dublin

"I think that Thursday's engagement between the taoiseach and the British prime minister is probably the most important political engagement that we have seen in the last 20 years," the former Stormont Education Minister said.

Speaking after a meeting with Taoiseach Bertie Ahern in Dublin, both Mr McGuinness and Sinn Fein president Gerry Adams stressed the importance of Thursday's talks between Mr Ahern and Tony Blair.

Tuesday's meeting was one of a series the taoiseach is holding this week in an attempt to revive the power-sharing assembly at Stormont.

The province's devolved institutions were suspended on 14 October 2002 following a row over allegations of IRA activity, including alleged spying within the Northern Ireland Office.

Before the meeting, Gerry Adams said he would be raising his concerns over recent speculation in the media of an imminent move by the IRA to restore confidence in the peace process.

He alleged most of the briefings were coming from the Dublin government.

Mr Ahern will meet SDLP leader Mark Durkan on Wednesday.

Dates for meetings with Ulster Unionist Party leader David Trimble and Tony Blair in London have not yet been finalised.

Delegation

An Irish Government spokesperson said the meetings would focus on areas "central to restoring trust and confidence among the parties in Northern Ireland".

Meanwhile, a Sinn Fein delegation will meet Secretary of State Paul Murphy on Tuesday to discuss the operation of the North-South bodies set up under the Good Friday Agreement.

Pat Doherty, Caoimhghin O'Caolain and Conor Murphy will attend the meeting at Castle Buildings, Stormont.

Mr Murphy said the party would be clarifying what progress had been made in the North-South Ministerial Council and in designated areas of co-operation such as agriculture and transport.

He said Sinn Fein also wanted to see what work had been done on the establishment of the All Ireland Parliamentary Forum and the All Ireland Civic Forum.

Six cross-border bodies were set up under the Agreement.