Talks being held in Belfast to resolve issues surrounding new proposals which would see the Irish tricolor fly over Stormont in Belfast, alongside the union flag when certain Irish dignitaries are in Northern Ireland have failed to find an agreement on the past parades and flags before the New Year’s Eve deadline.

US diplomat Dr Richard Haass and Harvard professor Meghan O’Sullivan are now considering returning to  Northern Ireland this coming weekend to try and complete an agreement.

The parties talked through the night on Christmas Eve, but they could not reach a solution. Seven hours of talks ended at around 4 a.m. on Tuesday without agreement, and Haass said "significant differences and divisions" remain.

The Associated Press reports Mr Haass saying "The work done on flags is quite disappointing by any measure," he said.

"But the other two areas have been, I believe, quite impressive and I believe it would be a real shame not to be able to turn that work into a reality."

Haass — who now will go back to the U.S. — insisted the process is "still alive" and said he might return to Belfast next weekend if reactions to a revised proposal indicate progress could be made.

"Will explore if a last push justified," he added on Twitter. "Hope so, as all would gain from pact."

Later outside the Stormont Hotel, Haas said: "I am not in the business of doing post mortems here because the patient is still alive."

The Democratic Unionists, the UUP, Sinn Fein, the SDLP and Alliance discussed four separate plans, each of which were vetoed through days of talks.

DUP Lagan Valley MP Jeffrey Donaldson said: "Obviously I think everyone is disappointed that we are not having an agreement at this stage.

"But we have to be realistic - there remain significant issues of difference across all three areas that were under negotiation.

"I think with further effort we are capable of closing the gap but it just didn't happen tonight."

Sinn Fein's negotiator, Gerry Kelly, said the party's team had been mandated by its ruling executive to try to secure agreement in the meeting.

"We are disappointed that we weren't able to do that," he said.

"Probably more important is that people watching this will be more disappointed if we can't bring this to some sort of conclusion in the few next few days and phases.

"When it came to a deal, I think we could have done it, (but) we didn't manage to do it."

According to The Irish Times  the proposal on flags is to establish a commission on identity, culture and tradition which would have until sometime in 2015 to report on a way forward on flags. It was also proposed that this commission would deal with the Irish language and a bill of rights for Northern Ireland.

On the past it is proposed that a single investigative body be created which would continue to inquire into Troubles-related killings. This would replace the Historical Enquiries Team and also take over historical investigative work currently conducted by the PSNI and the Police Ombudsman.