The Obama administration has urged politicians in Northern Ireland to compromise on a deal on parading, flags and dealing with the region's troubled past.
Five-party talks enter their final hours tomorrow in a last-ditch attempt to reach agreement on issues left over from the peace process.
Former US diplomat Dr Richard Haass has been leading negotiations in an effort to prevent a resumption of recent sectarian violence.
US National Security Council spokeswoman Caitlin Hayden said: "Initiating these talks demonstrated the commitment of the parties and people of Northern Ireland to move forward on tough issues. We are confident that a solution can be reached if there is political will on all sides.
"We call upon the leadership of the five parties to make the compromises necessary to conclude an agreement now, one that would help heal the divisions that continue to stand between the people of Northern Ireland and the future they deserve."
There has been an upsurge in recent bombings and attempts to kill members of the security forces by dissident republicans opposed to the peace process, which culminated in the 1998 Good Friday Agreement.
But measures intended to ease months of simmering resentment and violence are extraordinarily close to gaining support, Dr Haass has said, adding that the missing ingredient was not more time and urging politicians to grasp the opportunity to do a deal.
A session starting at 6am on Monday will bring six months of increasingly intense negotiations to a head after the conflict resolution expert cut short his Christmas break to kick-start one last round of crunch discussions.
Dr Haass and Harvard professor Dr Meghan O'Sullivan, who worked in post-conflict Iraq, were asked by Northern Ireland's ministerial executive in July to lead talks after a violent summer of parade and protest.
Serious loyalist rioting broke out a year ago after restrictions were imposed on the flying of the Union flag from Belfast City Hall.
This summer's marching season sparked riots after a decision was taken to reroute a loyal order parade away from a traditional scene of yearly violence in North Belfast.
The talks are intended to provide a framework for when contentious flags can be flown, for dealing with the victims of 30 years of violence which produced more than 3,000 lost lives and deciding whether perpetrators should face prison sentences or be asked to tell the truth to grieving relatives.
Politicians also hope for consensus on a new body to decide where members of the loyal orders and republicans can march.
Ulster Unionist leader Mike Nesbitt said the political negotiations in Belfast are "80 to 90% over the line".
"So there's not a lot left, but what is left is serious from our point of view," he said.
On Saturday Democratic Unionist Party (DUP) Northern Ireland First Minister Peter Robinson said parts of the proposed agreement were "unworkable".
Sinn Fein president Gerry Adams, whose party represents most nationalists, has voiced hope that a deal can be done and appealed to talks participants to overcome their differences.
Victims' group Relatives for Justice has lobbied over killings by members of the security forces during the 30-year Troubles.
It said: " Overall the key to the success of any process will undoubtedly be that of independence - the ability to be independently free from all political, security, and military/combatant vested interest influence and where the needs of all those bereaved and injured are paramount irrelevant of who caused the harms. And the ability to set terms of reference, remit and scope."
The Innocent Victims United umbrella group has been supported by some relatives of those killed by a dissident republican Real IRA bomb in Omagh in 1998.
Its statement claimed the Haass process supported the "warped" narrative that what occurred in Northern Ireland during 30 years of violence was a "war" as opposed to a terrorism campaign by the IRA.
"Those who showed restraint and who refused to bring the same death and destruction to the door of others must finally receive their day of justice," it said.
"They cannot continue to be sacrificed by a process which conveniently wants to 'airbrush' away the circumstances of their hurt and suffering."
A Historical Enquiries Team (HET) of detectives was established to investigate unsolved Troubles murders, but has run into controversy after an inspection accused it of treating security force killings differently from those by paramilitaries.
All parties agree that the views of victims should be integral to any process for dealing with the past, but it has been difficult to decide what that mechanism should be, whether limited immunity from prosecution should be offered to those who give information about shootings, bombings and other atrocities and what powers any new commission for investigating the past should have.
A replacement for the Government-appointed Parades Commission, which was heavily criticised by unionists after it rerouted a loyal order parade away from the nationalist Ardoyne part of North Belfast last summer following years of annual violence on July 12, is also thought to be under discussion.
The issue of where and when flags fly may be left to a separate process as parties have so far been unable to reach a common position.