UK Prime Minister Rishi Sunak has travelled to Belfast to sell his landmark agreement with the European Union to its toughest audience: unionist politicians who fear post-Brexit trade rules are weakening Northern Ireland’s place in the United Kingdom.

The UK and the 27-nation EU announced on Monday they had struck a deal to resolve a dispute over Northern Ireland trade that has vexed relations since the UK left the bloc in 2020.

The agreement will ease customs checks and other hurdles for goods moving to Northern Ireland from the rest of the UK that were imposed after Brexit to maintain an open border between the north and its EU neighbour, the Republic of Ireland.

The deal, dubbed the “Windsor Framework”, was hailed by London and Brussels as a breakthrough. But Northern Ireland’s British unionist politicians have yet to give it their blessing.

Their support is key to restoring Northern Ireland’s semi-autonomous government, which has been toppled by the trade feud, leaving 1.9 million people without a functioning administration.

Mr Sunak told the BBC the deal was “a huge step forward for the people of Northern Ireland” and he was confident politicians there would support it.

The Democratic Unionist Party, which had governed alongside Irish nationalists Sinn Fein in the power-sharing administration, walked out of the government a year ago to protest against the trade rules and has refused to return until they are scrapped or substantially rewritten.

Under Northern Ireland’s political system, power is shared between Irish nationalists and British unionists, and neither side can govern without the other.

DUP leader Jeffrey Donaldson said the party would “take our time” to pore over the details of the deal before delivering its verdict.

“We’re reasonable people, but we want to ensure that what the prime minister has said is matched by what is actually in the agreement itself,” he said.

Northern Ireland is the only part of the UK that shares a border with an EU member. When the UK left the bloc, the two sides agreed to keep the Irish border free of customs posts and other checks because an open border is a key pillar of Northern Ireland’s peace process.

Instead, there are checks on some goods entering Northern Ireland from the rest of the UK That angered British unionist politicians in Belfast, who say the new trade border in the Irish Sea undermined Northern Ireland’s place in the United Kingdom.

Mr Sunak said the new Windsor Framework “removes any sense of an Irish Sea border”, removing checks on the vast majority of goods.

It also gives Northern Ireland politicians a mechanism to challenge new EU trade rules that could apply in the region – a key unionist demand.

Business groups largely welcomed the deal, saying it would ease the burdens faced by companies and give Northern Ireland customers access to goods such as English sausages that were blocked under the original post-Brexit rules.

Some hardline pro-Brexit politicians in Mr Sunak’s governing Conservatives also were surprisingly positive.

The agreement was also welcomed by the White House, which said it was “grateful” the two sides could resolve the dispute.

-AP