Tony Blair has urged Prime Minister Theresa May to use her authority to help break the political deadlock in Northern Ireland.
Tuesday marks 20 years since the former British premier and his Irish counterpart Bertie Ahern sealed the Good Friday peace agreement, which largely ended decades of violence.
Mr Blair said he believed it was possible to resolve the current Stormont impasse, which has left the country without devolved Government for 15 months.
He told BBC NI's The Sunday News: "This requires the full focus of the Government."
He added: "At a certain point the authority of the Prime Minister is necessary in order to get people to move and to come into some form of alignment."
In 1998, the leaders of Northern Ireland's main parties - the DUP and some Ulster Unionists dissented - the British and Irish Governments and US special envoy to Northern Ireland George Mitchell brokered the Good Friday Agreement.
It led to the early release of paramilitary prisoners who had committed countless killings and was followed by decommissioning of terror weapons, fundamental reform of the Royal Ulster Constabulary (RUC) and the establishment of a devolved cross-community power-sharing government at Stormont.
In 2017, that administration foundered over a botched Government-run green energy scheme.
Divisions between the DUP and Sinn Fein over Irish language rights and addressing the legacy of Northern Ireland's violent past have prevented its resumption.
Mr Blair said: "I cannot believe it is not possible to find a way around it.
"It is very similar to the types of issues we used to deal with.
"It is not easy, and Brexit complicates things for a variety of reasons but... it is still worth doing."
Mr Ahern also called on Stormont's current political leaders to shift positions.
He told The Sunday News: "The art of politics is compromise, the art of politics is working together for the good of the people, the people that elect you, the people that trust you, this is what political leadership is about."