The Democratic Unionist Party, the main Protestant party in Northern Ireland and one of its biggest political forces, said on Tuesday that it was ready to return to power sharing after a boycott of almost two years had paralyzed decision-making in the region.
After an internal meeting that stretched into the early morning, Jeffrey Donaldson, leader of the party, known as the D.U.P., said at a news conference that he had been mandated to support a new deal, negotiated with the British government, that would allow his party to return to Northern Ireland’s governing assembly.
“Over the coming period we will work alongside others to build a thriving Northern Ireland firmly within the union for this and succeeding generations,” Mr. Donaldson said. He added, however, that the return to power sharing was conditional on the British government’s legislating to enshrine a new set of measures that had not yet been made public.
The announcement from the D.U.P., which represents those who want Northern Ireland to remain part of the United Kingdom, will be welcomed by many voters frustrated by the political stalemate, as well as by the British and Irish governments, which have both put pressure on the party to end the deadlock.
But it could also herald a seismic shift in the territory’s history, opening the door for Sinn Fein, the Irish nationalist party, to hold for the first time the most senior political role of “first minister” rather than “deputy first minister.”
Sinn Fein is committed to the idea of a united Ireland, in which Northern Ireland would join the Republic of Ireland, rather than remain part of the United Kingdom.
The breakthrough followed months of tense discussion between the D.U.P. and the British government aimed at bringing the unionists back into Stormont, the Northern Ireland assembly in Belfast that was launched as part of the Good Friday agreement that ended the region’s decades of sectarian violence, known as the Troubles.
Stormont cannot operate without the participation of the territory’s two leading parties, representing unionists, who are mainly Protestants, and nationalists, who are largely Roman Catholics.
The D.U.P. walked out in February 2022 in protest of post-Brexit trade rules, and since then, civil servants have kept the basic functions of government running.
But bigger decisions require the approval of Stormont, and Mr. Donaldson has been under growing pressure to end the boycott, not just from the British and Irish governments, but also from voters in Northern Ireland, where services including health care have been under acute pressure.
This month, tens of thousands of people took part in the biggest strikes in recent memory, as public-sector workers walked out in protest over their pay, which has lagged that of colleagues in the rest of the United Kingdom because of the political gridlock.
In December, the British government offered an additional 3.3 billion pounds for Northern Ireland on the condition that the D.U.P. returned to Stormont.
Mr. Donaldson, however, has also been pressed by hard liners in his own party to stand firm, and the decision to return to government could put him on a collision course with them.
In May 2022, Sinn Fein overtook the D.U.P. in legislative elections and became Northern Ireland’s biggest party. A few months before, the D.U.P. had withdrawn from power sharing in protest over post-Brexit trade rules, which imposed checks on some British goods entering Northern Ireland.
Unionists said those restrictions, enshrined in a deal called the Northern Ireland protocol, would drive a wedge between the territory and the rest of the United Kingdom, and called for the British government to all but overturn it.
In 2023, Rishi Sunak, Britain’s prime minister, struck a new deal with the European Union, known as the Windsor Framework Agreement, which wrested some concessions from Brussels. But they were not enough for the D.U.P.
The party’s reservations now appear to have been resolved after new negotiations the British government in London, paving the way for an end to almost two years of administrative deadlock.
Though many will welcome the prospect of the restoration of power sharing, any deal will still be a risk for Mr. Donaldson, since hard-line unionist critics oppose compromise.
One of them, Jim Allister, leader of the Traditional Unionist Voice party, said on Monday that his cause faced a “defining moment,” urging the D.U.P. not to agree to the post-Brexit trade arrangements. “It would be a point of no return,” he told reporters, “because that would be accepting that never again would Northern Ireland be a full part of the United Kingdom.”