The UK and Irish governments urged Northern Ireland’s rival parties to come together to resurrect its power-sharing executive after nationalist party Sinn Fein topped the voting in elections for the first time.
Sinn Fein, which seeks a united Ireland, became the biggest party in Northern Ireland’s Assembly with 27 of the 90 seats, beating the Democratic Unionist Party, which secured 25 seats.
It is the first time in Northern Ireland's history that an Irish nationalist party has topped the voting.
It is not yet known if Sinn Fein will lead a new government because of Northern Ireland's delicate power-sharing politics and continuing tussles over the legacy of Britain's exit from the European Union.
Sinn Fein's Vice President Michelle O'Neill now has the right to the post of first minister, but a government cannot be formed unless the largest unionist party agrees to join in the role of deputy first minister.
In February, the DUP's Paul Givan quit as first minister in protest against post-Brexit border arrangements, collapsing Northern Ireland’s Executive. His party has said it will not return to government unless their demands over the customs arrangements are met.
Leaders in London and Dublin said all parties must now re-establish the government as soon as possible.
Irish Prime Minister Micheal Martin said late on Saturday that "it is now incumbent on all political parties and elected representatives to deliver on their mandate."
"Power-sharing and principles of partnership, equality and mutual respect are at the heart of the Good Friday Agreement, through which peace has been secured and progress achieved for almost 25 years," he added. "A new power-sharing executive is vital for progress and prosperity for all in Northern Ireland."
In London, Northern Ireland Secretary Brandon Lewis said he will meet party leaders Monday to discuss how to re-establish a functioning government.
Mr Lewis said that the UK government would like to reach an agreement with the EU to resolve disputes over post-Brexit rules known as the Northern Ireland Protocol.
The DUP is strongly opposed to the rules, which have imposed customs and border checks on some goods entering Northern Ireland from the rest of the UK.
Unionists say the new checks have created a barrier between Northern Ireland and the rest of the UK that undermines their British identity.
Britain's Conservative government is trying to persuade the EU to agree to major changes, but negotiations have reached an impasse.
"The UK government's position is we want to secure a deal with the EU. We're very clear about that," Mr Lewis told the BBC.
“We have worked very hard on that for over a year now across a series of conversations. We made proposals. The EU haven't shown any flexibility."
Northern Ireland's delicate system, which splits power between the largest British unionist party and largest Irish nationalist party, was created by the 1998 Good Friday peace agreement that ended decades of Catholic-Protestant conflict.
If no power-sharing executive can be formed within six months, a new election may be triggered.