Rishi Sunak and the European Commission president are due to hold “final talks” on a new post-Brexit deal for Northern Ireland on Monday, Downing Street says.
The prime minister and Ursula von der Leyen will meet in Berkshire in the afternoon to discuss “complex challenges” around the protocol.
The UK wants to change the current agreement – which sees some goods checked when entering Northern Ireland from the rest of Great Britain.
A new deal has been expected for days.
Deputy Prime Minister Dominic Raab earlier said the UK and EU were “on the cusp” of a deal and that the EU had “moved” on some issues.
Downing Street released more details about the talks between Mr Sunak and Ms von der Leyen, which is set to take place around late lunchtime.
If a deal is reached, it would then be announced later on Monday, with the leaders holding a joint press conference after the cabinet has been updated.
The prime minister would then address the House of Commons.
Both Tory and Labour MPs have been told by their respective whips to come to Parliament on Monday.
Downing Street said: “The prime minister wants to ensure any deal fixes the practical problems on the ground, ensures trade flows freely within the whole of the UK, safeguards Northern Ireland’s place in our Union, and returns sovereignty to the people of Northern Ireland.”
There have been “hundreds of hours of talks” during the “intensive negotiations with the EU”, the spokesperson added, saying “positive, constructive progress has been made”.
The Northern Ireland Protocol was agreed under former PM Boris Johnson as part of the process of the UK leaving the European Union.
It means Northern Ireland has continued to follow some EU laws so that goods can flow freely over the border to the Republic of Ireland without checks.
Instead, goods arriving from England, Scotland and Wales are checked when they reach Northern Irish ports.
Critics, including Northern Ireland’s Democratic Unionist Party (DUP), feel this undermines the nation’s position within the rest of the UK as well as impacting trade.
The DUP has complained about what it calls a “democratic deficit”, with Northern Ireland being subject to EU rules while not having a say on them.
The party has prevented a Northern Ireland devolved government from forming, leaving it in political gridlock.
BBC chief political correspondent Nick Eardley said that while officials had been negotiating over the weekend, leader-level talks were needed to discuss the final details.
Sources in government have repeatedly said that not everyone will get everything they want from the deal – but the priority is addressing issues with the protocol and protecting the Good Friday agreement, our correspondent said.
There is no expectation in Westminster that the DUP will endorse the deal immediately and many believe it will not be enough to tempt them back to Stormont, he added.
Some Conservative MPs could also rebel against the government in any vote in Parliament, with Brexiteer Tories wanting lawyers to scrutinise the text.
One Tory told the BBC on Sunday night: “The bottom line is – if this doesn’t result in power sharing, it’s not a worthwhile agreement.”
Taoiseach (Irish Prime Minister) Leo Varadkar said he had been in contact with Ms von der Leyen on Sunday and “very much” welcomed her meeting with Mr Sunak.
He tweeted: “We should acknowledge the level of engagement between the UK Gov, the European Commission and the NI parties in recent months.”
His deputy, Micheal Martin, said there had been “very significant progress”, adding “a great effort” had been made to resolve issues.
“I would hope it can be brought to a conclusion, but that’s a matter for the UK and EU negotiating teams to call.”