Those who believe in peace and the Good Friday agreement "have to deliver the evidence before the eyes of the sceptics that it works", the President, Mrs McAleese, said in New York yesterday.
"They have got to recommit and prove that peaceful means do work," Mrs McAleese told a group of Irish journalists, emphasising that trust had been the main casualty of recent events.
She appealed to everybody who said they were committed to the Good Friday agreement "to galvanise that commitment and to reactivate that commitment with a new-found passion".
"The prize of peace, which has been so painstakingly built over the last four years and has been delivered well, is just too great and precious a gift to walk away from and not to be protected."
Mrs McAleese, on a two-day visit to the US, yesterday received an honorary doctor of law at the University of Delaware in Wilmington,
On Thursday, she was guest of honour at the annual Celtic ball in New York's Waldorf Astoria Hotel. She told some 600 patrons the peace process was going through a fraught time when disillusionment needed to be countered by a "profound rearticulation of the deep-rooted and shared desire for peace".