Sinn Féin president Gerry Adams has called on both governments and all political parties to build momentum in the peace process following a meeting with Tony Blair.
Meanwhile, unionist leaders have warned of a boycott on talks lasting at least two years following the announcement by the Provisional IRA that its armed struggle is over.
The British Prime Minister held separate top-level meetings with delegations from both Sinn Féin and the DUP in London on Friday.
Yesterday’s meetings were the first direct dialogue between Mr Blair and northern politicians since last Thursday’s historic IRA statement.
Speaking after the meeting, Gerry Adams insisted that the DUP could not be allowed to hold up the implementation of the Good Friday Agreement.
“There is no reason why there should not be devolved government back in place today or tomorrow,” Mr Adams said.
“While we are very clear on what needs to happen we have to accept that everyone needs to have an opportunity to absorb the import of the momentous decision and announcements by the IRA.”
Speaking to reporters outside Downing Street, Sinn Féin’s chief negotiator Martin McGuinness called on the DUP to “regain their nerve”.
“I think they have to realise that they have a mighty contribution to bringing peace to Northern Ireland and they have to play their part,” Mr McGuinness said.
“The ball game has changed, changed completely and I think forever.
“At some stage the DUP will have to respond to an agenda which is very clearly moving on without them,” Mr McGuinness added.
However, the DUP has said it is planning a “prolonged period of assessment” to determine whether the IRA had really given up its armed campaign.
Following talks in Downing Street, Ian Paisley accused the British government of having “caved in” to the IRA and given it “concession after concession” even though there was no real proof that the armed struggle was over.
“We are not going to have any discussions about devolution until the requirements Mr Blair set out are fulfilled by the IRA,” he said.
His deputy, Peter Robinson, added: “It will take a long period of time to make sure that they are gone and they are gone for good.”
Mr Paisley said he had presented a list of demands to the Prime Minister in what he described as a “blunt” meeting.
These included assurances relating to the British government’s announcement that it intended to disband the three home-based battalions of the Royal Irish Regiment, formerly the UDR.
Prime Minister Tony Blair rejected unionist accusations that the moves on demilitarisation were unjustifiable.
“These are things that are justified and actually have been justified for some time in security terms,” Mr Blair said.
Mr Blair was also at odds with the DUP over the verification of proposed IRA weapons decommissioning, and with the party’s threat of a two-year boycott of talks
Dr Paisley confirmed he was still seeking a photographic record of IRA decommissioning. However, Mr Blair said on Friday that “the only legal requirement” was that decommissioning be conducted by agreement with the International Commission on Decommissioning.