Decommissioning is not a precondition of the Belfast Agreement but an obligation of the accord, the Taoiseach told the Dail. Mr Ahern also said of the IRA's statement yesterday that "nothing has been said today or last night that has helped the situation".

Speaking during Taoiseach's Questions, Mr Ahern said the Government believed it was essential that the investigation into the murder of the solicitor Ms Rosemary Nelson be "thorough, independent and transparent". He also promised he would study new documentation on the 1974 Dublin and Monaghan bombings.

Describing the talks to resolve the impasse before today's deadline, Mr Ahern said there had been "serious engagement on crunch issues". The discussions were "down to a crucial point".

"I think I have got everybody to say, although some people might disagree, that decommissioning was not a precondition in the Good Friday agreement. Equally, however, everybody says it is an obligation under the Good Friday agreement.

"One of the things that annoys me when the agreement runs into difficulties is that a number of people - nobody in this House - express the view that that is not the case. They are the same people who say that George Mitchell is right. George Mitchell correctly gets credit for brokering the agreement.

"It is his interpretation - forget the Taoiseach's or anybody else's interpretation - that decommissioning is an obligation of the agreement. I am afraid that is game, set and match. If people want to give him the credit they cannot argue with his key point. That is his conclusion and I support it."

Handing weapons in to an RUC station was never a possibility. "We were talking about some way that, with a clear definition, I could at least negotiate on the terms of some date, some time within the terms of the agreement when we would have decommissioning. That is what we have been talking about. However, there must be some certainty."

He told Mrs Nora Owen, the Fine Gael deputy leader, in reference to the IRA statement yesterday, that he hated to comment on statements by people he was not in talks with. However, the parties he was dealing with "would say that it is probably useful that the decommissioning matter is not mentioned at all".

Mr Ahern added: "The commitment to keep guns silent and the other commitments by parties in the talks, be they the PUP or Sinn Fein, are useful and the commitment to the democratic system is useful. In terms of trying to help resolve the difficulties which Mr Blair and I face, I am afraid nothing has been said today or last night that has helped that position. We are still in a dilemma."

The issue of the Garvaghy Road and Portadown "really is an enormous problem which is wider than the Garvaghy Road or Portadown. It feeds into all the communities of the North, even wider than the nationalist community."

The Taoiseach referred to his meeting with Mr Paul Nelson, Ms Nelson's husband. Mr Nelson was determined that his wife's killers be brought to justice and that the truth about her murder would be established through an investigation which was thorough, independent and transparent.

The Labour Party leader, Mr Ruairi Quinn, asked if the Taoiseach believed that what the British government promised in terms of an independent inquiry "meets the required standard".

Mr Ahern said Mr Blair was trying to ensure that the tribunal would be transparent and independent and "to the satisfaction of everybody".

He said the Deputy Chief Constable of Norfolk could deal with the situation from a broader, international level. People with evidence would only talk to somebody they had absolute confidence in, an independent police force.