Ministers in the UK have received a new warning not to allow Britain's withdrawal from the European Union to jeopardise the Good Friday Agreement.
The Elders - a group of senior world figures originally brought together by Nelson Mandela - have expressed concern that the return of a "hard" border between Ireland and the North could undermine the peace process.
The group's chairman, former United Nations secretary general Kofi Annan, said: "The Good Friday Agreement has served Northern Ireland, the rest of the United Kingdom and the Republic of Ireland very well for the past 20 years.
"It was painstakingly achieved after complex negotiations and difficult compromises on all sides. Amid the wider political and economic uncertainty caused by Brexit, all stakeholders should place the preservation of peace and security as a high priority."
Mary Robinson, the former president of Ireland and a member of the group, said: "Peace in Northern Ireland was hard-won and needs to be protected.
"The Elders welcome the assertion by UK Prime Minister Theresa May of the paramountcy of the Good Friday Agreement, and the importance of ensuring that nothing should be done to allow the reimposition of a hard border.
"All governments and parties in all parts of the UK and Ireland must work to make this promise a reality."