Northern Ireland’s largest British union party has agreed to end a boycott that left the region’s population without a power-sharing government for two years and undermined the foundations of a 25-year-old peace treaty.

The breakthrough could see Belfast’s closed government restored within days – with the Irish nationalist party Sinn Féin holding the post of First Minister for the first time.

After a marathon meeting late in the evening, Democratic Unionist Party leader Jeffrey Donaldson said on Tuesday that the party’s executive had backed proposals for a return to government.

He said the arrangements reached with the UK Government in London “provide our party with a basis for nominating members to the Northern Ireland Executive, thereby ensuring the restoration of locally elected institutions”.

“The result was clear. The DUP was decisive. “I was tasked with moving forward,” Donaldson told reporters.

The breakthrough after months of inconclusive negotiations came after the British government last week gave Northern Irish politicians until February 8 to restore the Northern Ireland Assembly and local government or face new elections.

British Prime Minister Rishi Sunak called it a “positive step” to restore institutions and “save the people of Northern Ireland,” his spokesman said.

Sunak’s Northern Ireland secretary Chris Heaton-Harris told reporters that “all the conditions are now in place for the assembly to return” and that little resistance is expected in Westminster.

The agreement contained “significant changes… to ensure that our internal market functions properly,” he added, saying he did not believe it would require renegotiations with the European Union.

Reporting from Belfast, Al Jazeera’s Harry Fawcett said that while the deal had not yet been finalized, it was an important step towards power-sharing at Stormont, the seat of the Northern Ireland Assembly.

An approved deal would allow the DUP and nationalist pro-Irish Sinn Féin to elect a speaker for the assembly as early as next week.

Sinn Féin’s Michelle O’Neill would also become first minister – the first time a nationalist has held the post, after her party overtook the DUP at the last general election in May 2022.

Sinn Féin leader Mary Lou McDonald said this was “very significant” and she was optimistic the assembly would be back in business before the February deadline.

A central plank of the 1998 Good Friday Agreement, which ended three decades of sectarian violence against British rule in Northern Ireland, was to keep the border with EU member state Ireland open.

But after the United Kingdom decided to leave the EU and its borderless trading bloc after decades of membership, Northern Ireland found itself in a political deadlock.

The DUP resigned from government over its opposition to new trading rules introduced after the UK left the EU in 2020 that imposed customs checks and other hurdles on goods moving into Northern Ireland from the rest of the UK became.

The controls were introduced to maintain an open border between the north and the Republic of Ireland in the south. But the DUP says the new east-west customs border undermines Northern Ireland’s position in the UK.

In February 2023, the UK and EU agreed on a act to ease customs checks and other hurdles for goods moving into Northern Ireland from the rest of the United Kingdom. However, this was not enough for the DUP and they continued their boycott of the government.

The two-year break also put pressure on overstretched public services and led to a budget impasse with London.

That’s what triggered this Largest public sector strike in a generation this month after Northern Irish workers failed to receive pay rises given to others across the UK.

Steve Baker, a Northern Irish junior minister, sought to head off concerns that the changes could result in the UK having to follow certain EU rules again – which would anger Brexit supporters.

“There are no obligations to… bring GB (UK) into line with EU law; prevent GB from deviating from retained EU law; or to increase alignment in Northern Ireland beyond the strictly limited scope approved by Parliament,” he said on the social media platform X.

The Prime Minister of the Republic of Ireland, Taoiseach Leo Varadkar, said his government and the European Commission still need to see the final agreement to be sure that there will be no negative impact on the post-Brexit agreement for Northern Ireland, which was revised last year Good Friday has an agreement.

But after a “good” phone call with his British counterpart Rishi Sunak, Varadkar told the Irish parliament that he hoped a new government would be formed by February 8.