Northern Ireland’s political parties face an intensive day of talks as efforts to restore power-sharing at Stormont continue.
Round-table discussions will be begin at 14:00 BST on Tuesday. The deadline for a deal is Thursday.
However, it is believed parties need to reach agreement by Wednesday.
Irish Foreign Minister Simon Coveney said parties may have to consult supporters on a deal so talks would have to finish by Wednesday morning.
The DUP and Sinn Féin will meet on Tuesday morning ahead of round-table talks.
Stormont parties have been warned that if they cannot reach agreement on restoring the government, direct rule from Westminster could follow.
A sitting of the assembly has been scheduled for Thursday at noon which could involve the election of a first and deputy first minister – but only in the event of a deal.
Negotiations continued late into Monday night after a separate deal was announced between the Conservatives and the DUP at Westminster, resulting in an extra £1bn in public spending in Northern Ireland.
DUP leader Arlene Foster said that the agreement would help “boost the economy and invest in new infrastructure”.
Sinn Féin said the deal was a “blank cheque for a Tory Brexit” but any money coming to NI was a “good thing”.
Analysis: Enda McClafferty, BBC News NI political correspondent
A day that started with a deal at Downing Street ended with no sign that a deal is close at Stormont.
The DUP and Sinn Féin were locked in talks late into the night but it’s understood the parties are some way off reaching an agreement to restore power sharing.
Secretary of State James Brokenshire and Irish Foreign Minister Simon Coveney were briefed on the talks last night.
This morning all the party leaders will be involved in round-table discussions.
With the assembly scheduled to sit on Thursday, time is running out fast to reach a deal. It’s understood the parties are prepared for long and intensive talks over the next two days.
Speaking in London on Monday, the DUP’s Nigel Dodds said his party wanted to see the executive “up and running” and had set no “red lines, no pre-conditions”.
He added: “Let’s get on with the job, if Sinn Féin continue to mess about, I think they will pay a heavy price.”
Mr Dodds also said that the money agreed in the DUP-Conservative deal would be spent in Northern Ireland “regardless or not of whether the executive is in place”.
Sinn Féin’s John O’Dowd told the BBC Good Morning Ulster programme that there was a need to “implement outstanding agreements to get the executive up and going”.
‘Final 24 hours’
“I’m an optimist and realist,” he said. “We’re talking and while there’s talking going on there’s always hope we’ll see implementation of outstanding agreements.
“All of the parties tell us that’s there wish and ambition, certainly in terms of getting the executive up and running again, but we still have to bring others over the line in terms of implementation.”
He repeated that Sinn Féin want DUP leader Arlene Foster to stand aside while a public inquiry into the botched Renewed Heat Incentive scheme is ongoing.
UUP leader Robin Swann said that parties had now entered the final 24 hours of negotiations.
“Unless that intensification process delivers today and, I suppose, maybe even later into the night, I think we’re not looking at the return of the devolved institutions in this period and I think that’s a very dangerous place to be in.
“The concentration has to be on Sinn Féin at this moment in time because it seems to be them who are causing the stumbling blocks.”
The SDLP’s Colin McGrath said the party want to see “locally devolved institutions” but the DUP and Sinn Féin have questions to answer.
“We’re constantly told by the DUP and Sinn Féin it can be done in a day, told that the whole way through the process. So we have to ask at this stage, what is taking so long?”
The Alliance’s Party Stephen Farry said “to miss another deadline would be viewed by the public as being farcical”.
“The parties need to try and see if we ‘re going to move, if we’re going to have power sharing, and if not we’re going to have to deal with the consequences.”
Northern Ireland has been without a power-sharing executive since March and without a first and deputy first minister since January.
The institutions collapsed amid a bitter row between the DUP and Sinn Féin about a botched green energy scheme.
The late deputy first minister, Martin McGuinness, stood down, in a move that triggered a snap election.