20 years ago David Trimble and John Hume delivered the milestone agreement that came to be known as the Good Friday Agreement.
It is the first time that the three groups have issued a joint statement since the Loyalist ceasefire in 1994 and the statement comes one day before the 20-year anniversary of the Agreement, which was signed on April 10, 1998.
He added the problems in Northern Ireland were "immense" but the agreement was "the most incredible day".
He told an audience that included current political leaders, dignitaries and schoolchildren not to underestimate the work done by people of different persuasions.
"As I said at my party conference this weekend, if Good Friday 20 years ago was to be the final destination for slow learners - we can not allow it to fall victim to fast wreckers. You do smart things".
Mr Blair, whose media-savvy new Labour government had been accused of putting spin ahead of substance, had served up a juicy soundbite in the very same sentence he had warned against them.
Russia is successfully jamming American drones in Syria
The attack came as the final straw following weeks of sustained airstrikes that killed hundreds of people and injured thousands. In February, Israel confirmed that it had targeted the same airfield in Homs, after an Iranian drone entered Israeli airspace.
He said: "Let me make it clear, we are going to overcome that challenge and we should overcome it because preserving this agreement is really, really important".
There is an ovewhelming majority of people in Northern Ireland of all communities and all walks of life who understand that the significance of the Good Friday Agreement was not that all problems would be solved for all time.
The chairman of the 1998 talks, USA envoy to Northern Ireland George Mitchell, former Downing Street chief of staff Jonathan Powell, ex-Sinn Fein president Gerry Adams and former Ulster Unionist leader Lord David Trimble were also present at the event in Whitla Hall.
"The Good Friday Agreement will have to survive Brexit, and should survive Brexit, but it's a complication". It was codified by the British and Irish governments with the agreement of most of the major Stormont parties, with the notable exception of the Democratic Unionists.
There were also controversial proposals on the decommissioning of paramilitary weapons, the future of policing in Northern Ireland, and the early release of paramilitary prisoners.
Political leaders and those key to the drafting of the deal will meet in Belfast later.
The people in Northern Ireland voted 71% "yes" in a referendum on the ground-breaking compromise.
Senator Mitchell recalled to the packed auditorium how Mr Clinton had played a pivotal role during the negotiations, fielding 3am phone calls.