Former US diplomat Richard Haass has expressed his fears that Northern Ireland could slip back into the violence of its troubled past if politicians don't grasp the opportunity to deal with divisive issues.
Dr Haass chaired six months of cross-party talks last year in a bid to address flags, parades and the past which broke up without agreement.
Speaking to a Congressional committee in Washington, Dr Haass delivered a bleak and blunt assessment of Northern Ireland's future prospects if politicians continue to turn a blind eye to the most contentious problems.
He warned: "I don't see the society sowing the seeds of its own normalisation, of its own unity, if neighbourhoods and schools are still divided.
"What worries me in that kind of an environment, particularly where politics are not shown to be making progress, alienation will continue to fester and violence, I fear, could very well re-emerge as a characteristic of daily life.
"So it is premature to put Northern Ireland, as much as we would like to, into the 'outbox' of problems solved. I'd love for it to be there, but quite honestly it is not there yet."
Dr Haass expressed concerns that Northern Ireland, which he said was not a "normal society" yet, might take a step backwards into violence.
He said: "I do not want to see history repeat itself."
Dr Haass said there was a "sense of urgency" to deal with the three main issues at the centre of the negotiations he chaired.
"The passage of time will not by itself heal Northern Ireland's society or make it more normal or bring it together," he said.
"To the contrary, absent political progress, the passage of time will only create an environment in which social division intensifies, violence increases, investment is scared off, alienation grows, and the best and brightest leave to make their futures elsewhere."
Dr Haass also said it was premature to look at Northern Ireland as a model of peacebuilding.
He said: "Much of the world looks to Northern Ireland as a model of peacebuilding, and many in Northern Ireland like to be so viewed. But all this is premature."
Dr Haass also insisted the recent controversy over on-the-run republicans was not an excuse for political leaders to walk away from efforts to make progress.
On the letters sent to IRA suspects, he said: "I see nothing in their content that would justify walking away from the process that all five parties have been involved in."