The Northern Secretary has said political movement, goodwill between the parties and unequivocal support for policing must take place in 2006.
Peter Hain said these were essential if assembly elections due in May 2007 "were to have any meaning".
Meanwhile the Taoiseach said that if the forthcoming report from the Independent Monitoring Commission confirmed that the IRA was inactive, he and Tony Blair would try to restart all-party talks.
Mr Ahern, in an interview for BBC Radio 4 said: "Of course, I would like to see a united Ireland in my lifetime. I don't know whether I will or not. But what is more important is that we see peace and stability and people working together in Northern Ireland."
Mr Hain, in a statement to be released this morning, said political inertia was not in anyone's interest.
"Every year that passes without a locally-accountable assembly working through a power-sharing executive is a year in which the people of Northern Ireland have to live with a democratic deficit that cannot be justified in the United Kingdom of today," he said.
"Big decisions had to be taken in 2005 on education, infrastructure, health and public administration. Those decisions had to be taken by direct-rule ministers working in the best interests of Northern Ireland and its people.
"There will be more big decisions to be taken in the future, not least on policing and criminal justice, and those decisions should be taken by politicians elected by those who will be most directly affected by those decisions. That is the point of devolution."
In a reference to the lack of trust between the DUP and Sinn Féin, he added: "Unionists need to know that republicans are serious about the commitments given in the Good Friday agreement that they will work through exclusively lawful means.
"Republicans and nationalists need to know that unionists are serious about the commitments they have given that they will share power on a genuinely equitable basis.
"They have to persuade each other that a divided past can become a shared future."
Mr Ahern said he hoped a joint push with the British prime minister would lead to fresh talks in the first half of 2006, if the next IMC report confirmed the IRA was inactive.
"That will hopefully lead to the restoration of the assembly and executive," he said.
Mr Ahern was asked how hopeful the two governments were of securing a deal between the DUP and Sinn Féin.
"All we can do is use our powers of persuasion on the strength of the case," he said.
Sinn Féin's Martin McGuinness said the two governments needed to have a plan to restore the Northern institutions and should push for devolution next year.
Dublin and London "need to bring forward a plan in early 2006 to see the restoration of the power-sharing institutions in the North", he said.
The next IMC report is not expected to be published until early February. Mr Blair and Mr Ahern may well meet to decide on their next move shortly afterwards.