Negotiations to restore devolution in Northern Ireland will continue later with what is being billed as a new phase of intensified talks.
NI Secretary Karen Bradley and Irish Foreign Minister Simon Coveney are among those attending at Stormont.
On Sunday, the British and Irish PMs welcomed what they described as the “constructive engagement” shown by parties in recent weeks.
They said consensus had been reached on some issues but not on others.
In a joint statement, Prime Minister Theresa May and Taoiseach (Irish Prime Minister) Leo Varadkar said: “It is clear to us that the Northern Ireland political parties wish to see the institutions of the Belfast/Good Friday Agreement restored, but operating on a more credible and sustainable basis.”
They added that there was a “genuine but narrow window of opportunity to reach agreement in the immediate period ahead” and said it was essential to “intensify talks to this end”.
“We believe it is imperative that the parties now move without delay to engaging substantively on the shape of a final agreement,” the statement concluded.
Northern Ireland’s devolved government collapsed two-and-a-half years ago, after a bitter split in the power-sharing coalition led by the Democratic Unionist Party (DUP) and Sinn Féin.
What are the main sticking points in the NI talks?
- Irish language act: Sinn Féin and the DUP were thought to be close to a deal in 2018, but talks broke down on St Valentine’s Day due to a disagreement over a “standalone” Irish language act.
- Same-sex marriage: Sinn Féin has campaigned for it to be legalised but the DUP remains opposed. The last time MLAs voted on the issue, support for same-sex marriage achieved a narrow majority, but the DUP used a Stormont veto to block any change in the law.
- RHI scandal: Sinn Féin walked out Stormont’s power-sharing government in January 2017 in protest over the DUP’s handling of a green energy initiative known as the Renewable Heat Incentive (RHI) scheme. Failure to control costs led to a huge projected overspend and the scheme became the subject of a public inquiry which is yet to release its final report.
The latest effort to restore devolution began on 7 May, shortly after the killing of journalist Lyra McKee.
The 29-year-old was shot in the head while observing a riot in Londonderry.
Dissident republican paramilitary group the New IRA said its members killed her.
At her funeral, priest Fr Martin Magill was given a standing ovation when he asked why it had taken her death to unite politicians in Northern Ireland.
His words were followed by calls for a fresh round of talks to re-establish power-sharing.
The British and Irish governments were due to review progress in the talks at the end of May.
At the end of last week, Mr Coveney said there was a window in June to try to restore the Northern Ireland Assembly, but added the “stakes are high”.