The Irish foreign minister has warned that the Northern Ireland parties must be close to an agreement by Tuesday night in their talks to restore power-sharing.
The parties were holding further talks at Stormont on Monday evening.
They have until Thursday to reach an agreement.
Irish Foreign Minister Simon Coveney said that time was running out and both the DUP and Sinn Féin would have to be prepared to compromise.
They were holding talks on Monday night, with the leaders of all the main political parties in Northern Ireland expected to be involved in round-table discussions on Tuesday.
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.
Earlier on Monday, it was announced that a deal between the Conservatives and the DUP includes an extra £1bn in public spending for Northern Ireland.
‘Run out of time’
“There are some big political issues to be addressed this evening,” Mr Coveney said.
“If we’re going to get that done, both parties [the DUP and Sinn Féin] need to be willing to move towards each other’s position to try and accommodate each other.
“If that happens and we make significant progress on the issues that are separating the two large parties, then I think we can have a very constructive day tomorrow to try and include the SDLP, Alliance and the UUP, who have real issues also that need to be part of an agreement if we’re going to have an executive that involves all five parties.”
Mr Coveney added: “We’re going to need to be close to a final agreement by late tomorrow evening, if not we start to run out of time, because parties will have to go back to check with their support bases or their executives or whatever support processes they need to be able to sign up to a full deal.
“We’ll have a much clearer picture by this time tomorrow as to where we’re at.”
DUP leader Arlene Foster returned to Belfast from London earlier on Monday. She said she was “delighted” with the agreement reached to prop up Theresa May’s minority government.
Addressing the talks to restore devolution, the DUP’s Nigel Dodds said: “We want to see the executive up and running, we haven’t set any red lines, no pre-conditions, lets get an executive up and running.
“Let’s get on with the job, if Sinn Féin continue to mess about, I think they will pay a heavy price.”
However, Sinn Féin’s John O’Dowd said: “All outstanding issues are yet to be resolved; until we agree everything, nothing is agreed.
“There’s a lot of talking yet to be done in terms of Stormont Castle if we are going to reach an agreement by Thursday.”
SDLP leader Colum Eastwood said it was time to “stop playing games” and form an “inclusive executive” to make sure the £1bn was “spent properly for all our benefit”.
He said it would be “very dangerous” if the money was spent by a Tory party “under the thumb of the DUP”.
Robin Swann, Ulster Unionist Party leader, said NHS waiting lists were spiralling out of control and schools did not know whether they had a budget for next year because of financial uncertainty.
He said the ball was in Sinn Féin’s court now the terms and conditions of the DUP-Conservative pact were known.
The Alliance Party’s Stephen Farry said Monday evening and Tuesday would be the “critical phase” of the talks.
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.