Round-table all-party talks aimed at resurrecting political powersharing have been held at Stormont.
Tuesday is a key day in negotiations involving the five main Northern Ireland parties and the UK and Irish governments, with the outcome hinging on whether the two biggest parties - the Democratic Unionists and Sinn Fein - can resolve their differences.
Both parties were involved in late-night discussions at Stormont Castle on Monday.
The deadline for an agreement to establish a new coalition ministerial Executive is Thursday, when the devolved Assembly in Belfast is scheduled to sit to nominate ministers.
Outstanding issues include Sinn Fein's demand for legislative protections for Irish language speakers and the party's insistence that DUP leader Arlene Foster cannot return as First Minister while a public inquiry into a botched green energy scheme is ongoing.
Mrs Foster was forced from office in January when Sinn Fein's Deputy First Minister, the late Martin McGuinness, quit in protest at the DUP's handling of the ill-fated Renewable Heat Incentive scheme.
His move triggered a snap Assembly election in March. A number of attempts to restore powersharing in the wake of that poll floundered, with three UK Government deadlines for a deal having already been missed.
Civil servants have been running Stormont departments since March.
While the peace process is littered with examples of apparently firm political deadlines being broken, Northern Ireland Secretary James Brokenshire has insisted Thursday's 4pm cut-off point is immovable.
A form of direct rule from London is likely to be reimposed in lieu of a deal.
It remains unclear what impact the DUP's Westminster parliamentary deal with the Conservative Party will have on efforts to restore powersharing.
While rival Stormont parties have largely welcomed the additional £1 billion investment flowing from the confidence and supply agreement, concerns have been raised as to whether the UK Government has fatally compromised its stated commitment to impartiality in its dealings with Northern Ireland parties.
Sinn Fein's John O'Dowd said he is not sure whether a deal can be struck.
"I am an optimist and a realist," he told BBC Radio Ulster. "When there is talking going on, there is always hope."
DUP deputy leader Nigel Dodds has made clear his party has no "red lines" and said he wants to see an Executive up and running.
Irish foreign affairs minister Simon Coveney has said the "heavy lifting" needs to be done on Tuesday.