The Good Friday Agreement was the "work of genius" and a "precious gift", former US President Bill Clinton has said.
Speaking at a major conference in Belfast to mark the 20th anniversary of the historic 1998 peace accord, he urged the people of Northern Ireland to "inspire" the world again.
He said: "The Good Friday Agreement is the work of genius that's applicable if you care at all about preserving democracy.
"Because it called for a real democracy, majority rule, minority rights, individual rights, the rule of law, the end of violence, shared political decision-making, shared econpmic benefits, shared special relations, maintained the relationship with the United Kingdom, expanded the relationship with the Irish Republic and then let the future take its course."
Mr Clinton, who was later given the Freedom of Belfast, shared an hour-long panel discussion with former UK prime minister Tony Blair and Irish taoiseach Bertie Ahern - among the architects of the historic agreement - at an event at Queen's University Belfast.
He told an audience that included current political leaders, dignitaries and schoolchildren not to underestimate the work done by people of different persuasions.
"These people gave you a gift," he said. "People who lost loved ones and bore scars; the women's groups; everybody, they gave you a gift. Make the most of it. It is a precious gift.
"In the process, remind the world that democracy is better than dictatorship. Remember you inspired the world 20 years ago, you can do it all over again because the rest of the world continues to do foolish things. You do smart things."
Meanwhile, Mr Blair described Brexit as a "profound mistake" and warned of challenging consequences.
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.
"But those people who are either disdainful of the challenge or dismissive, this is going to require real focus and hard work because we cannot return to a hard border between north and south, it would be a disaster for the agreement and for the relationship between the Republic and the UK, and therefore for the people of Northern Ireland."
The chairman of the 1998 talks, US 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 largely ended the 30-year conflict which claimed more than 3,000 lives. 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.
The accord included the early release of about 500 paramilitary prisoners within two years even though IRA arms had not yet been destroyed.
Prisoner releases almost torpedoed the agreement in the final frantic hours before it was signed on April 10 1998 - Good Friday.
The deal also covered the re-establishment of devolved powersharing at Stormont and establishment of cross-border political bodies with the Republic, and led to a root-and-branch reform of the Royal Ulster Constabulary (RUC) into the Police Service of Northern Ireland (PSNI).
Paramilitaries undertook to destroy weapons and the IRA did so in 2005.
It enshrined the principle of consent - that Northern Ireland's constitutional position as part of the UK would only change if a majority in the region voted for it - while at the same time offering provisions that legitimised nationalist aspirations to strive for a united Ireland.
The agreement won the overwhelming support of a majority following referendums in both parts of the island and served as a blueprint for how to solve conflict around the world.
Twenty years later a ministerial executive at Stormont has not sat for more than a year in a dispute over the status of the Irish language, gay rights and dealing with the legacy of the past.
Senator Mitchell recalled to the packed auditorium how Mr Clinton had played a pivotal role during the negotiations, fielding 3am phonecalls.
Mr Clinton added: "By creating that space for the identity, and the interest and value of all the people involved in a framework which protected democracy and let future demographic, political and economic changes take Northern Ireland wherever it would go, it was a work of genius.
"In a world today where there are people who are aggressively trying to destroy the very idea of popular democracy, it embodied everything that I believe works best.
"Do not underestimate the value of the fact that this was done by people from different parties, of different persuasions and not one damn time in the whole process did anyone ever suggest that democracy itself should be abandoned; that the results of elections should not be respected, that some people's votes should be denied, discredited or that facts were not facts."