David Cameron's plea to the Stormont parties as he and Taoiseach fly in to broker a deal
The Prime Minister has warned that it is "crunch time" in the marathon talks to save Stormont.
Ahead of jetting into Belfast today, David Cameron said: "If we fail to reach an agreement now, with a cycle of elections approaching, a great opportunity will have been lost."
Writing in the Belfast Telegraph, the Prime Minister said the credibility of the devolved administration was on the line in the talks process, which is now in its ninth week.
The DUP last night said failure to reach agreement would threaten the survival of the institutions at Stormont.
But Mr Cameron and Taoiseach Enda Kenny will be pushing for a breakthrough when they join the local parties this afternoon.
Mr Kenny has raised hopes of a deal with talk of restoring £400m in investment on the A5 road. The upgrade would link two parts of the Republic - Donegal and Monaghan - via a dual carriageway through the southern part of Northern Ireland.
Mr Cameron is also expected to be asked for a financial package to ease Northern Ireland's financial woes. He has given no hint of what that might be, but writing off fines we have already accrued for failing to introduce welfare reform may be part of it, according to local political sources.
Another carrot the Prime Minister is offering is the devolution of corporation tax-setting powers to Northern Ireland. The Executive parties want this because they believe that lowering the tax on business profits will build up our flagging private sector by attracting foreign multinationals seeking a base in Europe.
Mr Cameron says: "There is an enormous amount at stake as we roll up our sleeves for what we hope will be the conclusion of this process. I want to see a Northern Ireland where politics works, the economy grows and society is strong; a Northern Ireland for the whole community.
"Yet today, the credibility and effectiveness of the devolved institutions is on the line."
He told local political leaders that he "was confident they share a genuine desire to reach an agreement", and added: "Time and again they have stepped up to the plate. Along with the UK and Irish governments, the time to do so again has arrived."
DUP negotiator Jeffrey Donaldson said failure to agree would threaten the survival of Stormont, but added his party did not anticipate the talks collapsing.
"We are not planning for failure," he said. "We are planning for success. We are working night and day to close the gap and resolve the issues. The budgetary issues are absolutely critical; if we can't get the budget right it is impossible to deliver the other elements of any agreement."
Sinn Fein's Conor Murphy said the opportunity to get an agreement must be seized.
"There is still substantial work to be done," he said. "The Taoiseach and the British Prime Minister need to contribute in a meaningful and substantial way to resolving the difficulties facing the political process."
A degree of positioning has been going on among politicians, especially the unionists. The TUV, Ukip and PUP have all pulled out of a unionist coalition on parades after accusing the DUP and UUP of doing secret deals with Sinn Fein.
And fears are growing that the UUP could leave the main talks. Party leader Mike Nesbitt said: "I think we have to do something significant by the weekend, and yes, it should be the budget, but we are being excluded from the budget talks. That is a mistake and it doesn't bode well for collective government for the future."