Bill Clinton has dubbed Brexit an "identity crisis" and has said the current "paralysis" in Northern Ireland poses significant dangers to democracy.
The former US president has pleaded with the Irish people not to let democracy and peace slide into the "hell of the Troubles", especially in the context of Brexit.
Speaking at an event to mark 20 years of the Good Friday Agreement in UCD tonight, President Clinton said the deal still remains a "beacon of hope", but warned that the Northern Ireland economy has already been impacted by the lack of an Executive.
On Britain's exit from the EU, he said: "What's going to happen with Brexit? In the end it's still an identity crisis, no one will drop off the face of the earth with any of the reasonable compromises that are being discussed."
President Clinton, who will travel to Belfast today, said: "My first plea is: This thing has lasted don't let it go, and you can't let it go by doing nothing."
He said that one of three things could now happen in Northern Ireland, which has been without an Assembly for more than a year.
"Or, two, you can stay in purgatory, where you got denied dreams and broken hopes and you’ll just rock along, caught on a sea of lost chances. If you do that, slowly you will begin to lose a democracy in the North. And everything that could happen and the cooperation between Northern Ireland and the republic, the larger Europe and the UK.
"Or three, everybody can rear back, settle down and make a new beginning. Whatever compromises have to be made to minimise the damage of Brexit, to keep the markets as open as possible, and share the Government.
He added that it is so easy to "underestimate the fragility" of the situation which many now take for granted.
"So when Brexit happens, and then you can’t make a deal on these other things and then the Government goes down, then everybody's temptation is to double down and bargain harder."
He added that if compromises are not made, people would have to think about what might happen to the "larger politics and the Irish republic or in the UK, the whole thing".
Mr Clinton said: "The Irish peace was born out of weariness of children dying and of lost chances, the further you get away from that the easier it is to take the absence of bad for granted and to live in this purgatory where we are now. It's a big mistake.
Looking back at the Good Friday deal, he said "the real credit " for the agreement has to go to the "leaders who made the decisions along the way" citing a number of people including Ian Paisley, Martin McGuinness, Gerry Adams, Bertie Ahern, Tony Blair, John Hume as well as community and women's groups.
Commending John Hume and David Trimble he said they put their political parties at risk "for the young people and the future".
President Clinton said he was "first captivated" by the Troubles of Northern Ireland as a student when he wondered - especially given his Irish roots on his mother's side - would he ever see it come to an end.