Tony Blair has urged British 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 former Taoiseach 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 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 Féin 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."
A UK Government spokesman said: "This Government's support for the Belfast Agreement and its successors as the basis for devolution in Northern Ireland remains steadfast.
"As we mark the 20th anniversary of the Agreement, we are totally committed to the restoration of the devolved institutions, working intensively with the parties and the Irish Government to achieve that.
"Throughout the past year the Prime Minister has been heavily involved in the political process. She has led frequent discussions with Northern Ireland's political leaders and Taoiseach Leo Varadkar, including in Belfast in February.
"The Prime Minister and the Secretary of State will continue to do whatever is necessary to see devolved government restored and the Agreements implemented in full."