Tony Blair and Bertie Ahern, the Irish Prime Minister, have set a deadline of lunchtime today for a deal between the rival political leaders in Northern Ireland on policing and power sharing in the Assembly.
Mr Blair's official spokesman said the two premiers may put "best guess" proposals to the Northern Ireland parties for achieving devolution if the politicians fail to reach agreement.
The two parties involved, Sinn Fein and the Democratic Unionist Party (DUP), will then have until 24 November to say whether they will sign up to the proposals and revive the Northern Ireland Assembly.
The spokesman said there would be no further talks after today.
"In the end it will be the two governments which will have to call it," he said. "The message that the two Prime Ministers are giving to the two sides is that this is it. These issues are not going to change.
"We recognise that they are difficult but this is it. It is time for people to make up their minds. People know what the consequences are if they don't agree but if we do cross this river, we are in a different place."
Downing Street believes the difficulties over policing and power sharing can be resolved but that Sinn Fein and the DUP are keen to avoid being seen as the first to make a concession.
"The core issues remain power sharing and policing but it is the two governments' view that the DUP are prepared to share power with Sinn Fein," Mr Blair's spokesman said. "There are issues still to be addressed but on the basic principles they are prepared to move. It is also the Government's view that Sinn Fein are prepared to engage on policing."Reuse content