In the North, talks chaired by US diplomat Richard Haass have been suspended.
It was hoped agreement could be reached on contentious issues including flags and parades before Christmas.
Gerry Adams tweeted his disappointment shortly before 4am saying, "Talks suspended 4 Christmas. Good progress made. Disappointed agreement not concluded. Issues aren't going away".
The talks, involving the North's five main political parties, will resume on Friday 27th December.
