Overnight talks at the Stormont Hotel, Belfast, have failed to resolve peace process issues in Northern Ireland.
Divisions that triggered widespread rioting in Northern Ireland this year remained after seven hours of negotiations that ended early on Tuesday morning.
Richard Haas, the director of New York-based Council on Foreign Relations and former Northern Ireland envoy for US President George W Bush, led the talks involving Stormont's five Executive parties.
It was hoped that a compromise would be made by Christmas on areas including: parade routes, the use of British and Irish flags and emblems, and remembering Northern Ireland’s dead from the decade’s long conflict.
After he emerged from the meeting, Dr Haass said: “I am not in the business of doing post mortems here because the patient is still alive.”
He added that he and co-chair Dr Meghan O'Sullivan, a US foreign affairs expert, will consider returning before the New Year if they are convinced a deal is still possible.
The parties will be sent questions from the US, from which Dr Haas and Dr O’Sullivan will produce the fifth set of draft proposals.
Shadow Northern Ireland Secretary Ivan Lewis said: “The lack of an agreement before Christmas is clearly disappointing."
He added:“The priority now is for all Northern Ireland's political leaders to demonstrate their continued commitment to this process by asking Richard Haass and Meghan O'Sullivan to return at the earliest opportunity."
“The Haass talks offer the best hope for dealing with contentious issues such as the past, parades and flags, which continue to be obstacles to the development of a shared future for Northern Ireland," he said.