Crunch talks to restore powersharing in Northern Ireland are set to intensify as a deadline for agreement looms.
Politicians have until Thursday afternoon to establish a new coalition Executive at Stormont.
With a deal required to be in place ahead of Thursday's scheduled Assembly sitting to nominate ministers, Tuesday will be a key day in the negotiation process.
While the process involves the five main Stormont parties and the UK and Irish Governments, its fate hinges 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.
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 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 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 was not sure whether a deal could 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 made clear his party had no "red lines".
"We want to see an Executive up and running, we haven't set any red lines, no pre-conditions," he said on Monday night.
"Let's get the executive up and running. Let's get on with the job. If Sinn Fein continue to mess about I think they will pay a heavy price."
Irish foreign affairs minister Simon Coveney said the "heavy lifting" needed to be done on Tuesday.
"If we are going to get that done, both parties need to be willing to move towards each other's position to try to accommodate each other," he said.
He added: "There are political choices to be made."