Downing Street says Rishi Sunak and the president of the European Commission are due to hold “final negotiations” on a new Brexit deal for Northern Ireland on Monday.
The Prime Minister and Ursula von der Leyen will meet in Berkshire in the afternoon to discuss the “complex challenges” surrounding the protocol.
Britain wants to change the current deal – which checks some goods entering Northern Ireland from the rest of the UK.
A new deal has been expected for days.
Deputy Prime Minister Dominic Raab said earlier that Britain and the EU were “at the bottom” of a deal and that the EU had “moved” on some issues.
Downing Street released more details about the conversation between Mr Sunak and Ms von der Leyen, which is set to take place over a late lunch.
If a deal is reached, it will be announced later on Monday, with the leaders holding a joint press conference after updating the cabinet.
After that, the Prime Minister will address the House of Commons.
Both Tory and Labor MPs have been asked by their respective whips to come to Parliament on Monday.
Downing Street said: “The Prime Minister wants to ensure that any deal addresses practical issues on the ground, ensures the free flow of trade across the UK, protects Northern Ireland’s place in our Union, And return sovereignty to the people of Northern Ireland.”
There have been “hundreds of hours of discussions” during “intense discussions with the European Union”, the spokesman added, adding that “positive, constructive progress has been made”.
The Northern Ireland Protocol was agreed under the leadership of former Prime Minister Boris Johnson as part of the UK’s exit from the European Union.
This means that Northern Ireland continues to follow some EU rules allowing goods to pass freely across the border to the Republic of Ireland without checks.
Instead, goods from England, Scotland and Wales are checked when they arrive at Northern Irish ports.
Critics, including Northern Ireland’s Democratic Unionist Party (DUP), feel it harms the country’s standing in the rest of the UK, as well as affecting trade.
The DUP has complained about what it calls a “democratic deficit”, with Northern Ireland subject to EU rules while having no say over them.
The party has blocked Northern Ireland’s devolved government from forming, leaving it in political disarray.
Our correspondent said government sources have repeatedly said that not everyone will get everything they want from the deal – but the priority is to fix problems with the protocol and protect the Good Friday Agreement.
He added that there was no expectation in Westminster that the DUP would ratify the deal immediately and many believed it would not be enough to lure them back to Stormont.
Some Conservative MPs may even rebel against the government in any vote in parliament, with Brexiteer Tories wanting lawyers to investigate the text.
One Tory told JEE News: “The bottom line is that if it doesn’t result in devolution, it’s not a beneficial deal.”
Taoiseach (Irish Prime Minister) Leo Varadkar said he was in touch with Ms von der Leyen on Sunday and he “very much” welcomed her meeting with Mr Sunak.
He tweeted: “We must acknowledge the level of engagement between the UK Government, European Commission and NI parties in recent months.”
His deputy, Michael Martin, said “very significant progress has been made”, adding that a “huge effort” had been made to address the issues.
“I would hope that it will be brought to a conclusion, but that is a matter for the UK and EU negotiating teams to call.”
