LONDON (AP) — The U.K, the European Union and Northern Ireland’s bitterly divided political parties said Friday that progress was being made on resolving a post-Brexit trade dispute that brought economic headaches and political turmoil to the region.

A flurry of political and diplomatic activity signaled a potential breakthrough after months of talks and political gridlock. British Prime Minister Rishi Sunak flew to Belfast for talks with political leaders, and Foreign Secretary James Cleverly met EU chief negotiator Maroš Šefčovič in Brussels.

“Intensive work continues,” Cleverly tweeted. Šefčovič posted: “Constructive engagement. Good progress.”

Sunak is also due to discuss Brexit with other European leaders this weekend on the margins of the Munich Security Conference in Germany.

Any deal faces a tough audience: unionist politicians who want Northern Ireland to remain part of the U.K. collapsed the Belfast power-sharing government almost a year ago because of their opposition to the existing trade arrangements with the EU.

However, Jeffrey Donaldson, leader of the biggest unionist group, the Democratic Unionist Party, was unusually upbeat after his meeting with Sunak in Belfast.

“On some very important issues, I think there has been real progress, but there remain some outstanding issues that that we need to get over the line,” Donaldson said. “We will then examine the final text of any agreement and come to our decision.”

Irish nationalist party Sinn Fein generally approves of the post-Brexit trade rules. But party leader Mary Lou McDonald said Friday it was “very much game on” for a deal to resolve the dispute over them.

“It’s clear now that significant progress has been made, and we’re very heartened by that,” she said.

Northern Ireland is the only part of the U.K. that shares a border with an EU member nation, the Republic of Ireland. When the U.K. left the bloc in 2020, the British government and the EU agreed to keep the Irish border free of customs posts and other checks because an open border is a key pillar of the peace process that ended 30 years of violence in Northern Ireland.

Instead, there are checks on some goods entering Northern Ireland from the rest of the U.K. British unionist politicians there are fiercely opposed to the arrangements, known as the Northern Ireland Protocol. Unionists say the new trade border undermines Northern Ireland’s place in the United Kingdom, and are refusing to return to government until the trade rules are redrawn.

Britain has sought to change the agreement to eliminate most of the customs checks. For months, U.K.-EU talks went nowhere in an atmosphere of mistrust and recrimination. Britain threatened to unilaterally rip up parts of the Brexit agreement, and the EU accused the U.K. of failing to honor the legally binding treaty it had signed.

But the mood has improved since Sunak, a pragmatic supporter of Brexit, took office in late October, replacing pugnacious predecessors Boris Johnson and Liz Truss, who delighted in riling the EU.

The U.K. hopes to resolve the dispute and restore Northern Ireland’s government before the 25th anniversary in April of Northern Ireland’s 1998 Good Friday peace accord. The British government hopes U.S. President Joe Biden will visit to mark the peace milestone.

However, any compromise by Sunak is sure to anger staunch Brexiteers, who form a powerful faction inside the prime minister's Conservative Party.

The thorniest issue is the role of the European Court of Justice in resolving any disputes that arise over the rules. That role was agreed by Britain and the EU in the Brexit divorce deal, but the DUP and Conservative Brexiteers insist the European court must have no jurisdiction in U.K. matters.

Irish Prime Minister Leo Varadkar said a deal was “not there yet” but he was “quietly confident” one would be struck.

“I do believe the prospect is there of having an agreement possibly within a week," he said.

Follow AP’s coverage of Brexit at https://apnews.com/hub/brexit and of British politics at https://apnews.com/hub/british-politics