Rishi Sunak is poised to unveil a Brexit deal with the EU on Monday that will overhaul Northern Ireland’s trading arrangements and end a bitter dispute between the two sides.

Although the UK prime minister plans to seal an agreement with Brussels, he still faces a political battle to win over Eurosceptic Conservative MPs and Northern Ireland’s Democratic Unionist party, which has hobbled the region’s devolved government.

Ursula von der Leyen, the European Commission president, will travel to Windsor on Monday morning to hold talks with Sunak aimed at finalising the Brexit deal to revamp Northern Ireland’s trading regime. People briefed on the proposed agreement said it would run to more than 100 pages.

Barring any last-minute hitches, Sunak and von der Leyen will hold a press conference before the prime minister heads to the House of Commons for a statement on the agreement.

“For us, the deal is basically there,” said one EU official. “Now it is a question of getting it over the finishing line.” One UK official added: “It feels like we’re basically there now.”

A deal would settle the dispute arising since the UK left the EU single market and customs union in 2021 via changes to the implementation of the Northern Ireland protocol, which sets out the region’s trading regime and was part of the Brexit agreement finalised by Boris Johnson in 2019.

The proposed agreement is designed not only to restore devolved government in Northern Ireland but also to improve the UK’s relations with the EU and the US, where Joe Biden’s administration has expressed concerns.

Pro-Britain parties in Northern Ireland have objected to how the protocol treats the region differently to the rest of the UK, while businesses complained of unnecessary bureaucracy.

The proposed deal is due to reduce checks on goods shipped from Great Britain to Northern Ireland, while also seeking to address Tory concerns over the role of the European Court of Justice in overseeing the protocol.

The agreement is expected to aim to reduce the influence of the European court in Northern Ireland but keep it as the ultimate arbiter of disputes about EU law.

Sunak’s deal is also expected to focus on the DUP’s concerns that Northern Ireland, by remaining in the EU single market for goods after Brexit, falls under Brussels’ rules.

This could be partly fixed by giving the devolved assembly at Stormont a bigger say on the EU rules.

People familiar with the deal said arrangements had also been reached to enable pets to travel freely between Great Britain and Northern Ireland without the need for microchips and passports.

EU diplomats hailed the apparent breakthrough on overhauling Northern Ireland’s trading arrangements.

“This is the closest we’ve been to putting the issues with the protocol to bed, which would allow us to move the relationship with the UK into a much more constructive framework,” said one diplomat.

Sunak is due to brief his cabinet about the deal on Monday and is likely to secure victory in any parliamentary vote about the agreement because Labour has signalled that it will support it.

The prime minister’s allies said the number of Tory MPs opposed to the deal could be limited to about 30.

But Sunak might still face a showdown with the DUP if it refuses to accept the agreement and continues to boycott the Stormont assembly.

The DUP last year forced the collapse of Northern Ireland’s devolved government in protest at how the protocol creates a de facto border in the Irish Sea and requires checks on goods coming to the region.

Jonathan Buckley, a DUP member of the Stormont assembly, tweeted that the party would judge any deal “wholly on its specific legal content”. “Getting it wrong will only deepen divisions,” he said.

The European Research Group of pro-Brexit Tory MPs is planning to closely scrutinise the agreement between Sunak and the EU, and consult with the DUP.

Mark Francois, ERG leader, said the DUP would not accept a Brexit deal where EU law was superior to UK rules in Northern Ireland. “We have to get rid of EU law in Northern Ireland,” he added.

But Sir John Major, the former Conservative prime minister, said the European Court of Justice would only have “tiny, partial and occasional” involvement over legal disputes in Northern Ireland.