The leaders of the UK and EU were holding "final talks" on Monday to seal a Northern Ireland trade deal after months of haggling over Brexit.
European Commission president Ursula von der Leyen said the UK and EU were on the brink of a "new chapter" as she arrived in Britain for talks with Prime Minister Rishi Sunak.
She will meet King Charles as part of her trip, despite concerns such a meeting would drag the king into politics. Buckingham Palace said it was normal for him to meet visiting leaders.
Her meeting with Mr Sunak took place near the royal Windsor Castle, with any Brexit deal potentially labelled the Windsor Agreement.
If a deal is reached, Mr Sunak is expected to brief his Cabinet, hold a joint press conference with Ms von der Leyen and deliver a statement in the House of Commons.
“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," Downing Street officials said.
Mr Sunak faces a tough battle to sell any deal to fellow Conservatives and to unionist MPs from Northern Ireland, with the 25th anniversary of the Belfast, or Good Friday, peace agreement looming large.
A former leader of the Ulster Unionist Party, Steve Aiken, told The National there was "no trust" between the UK government and Northern Irish businesses.
"They are talking over Northern Ireland. They are not talking to Northern Ireland,” Mr Aiken said of the UK and the EU.
"The reason the Belfast Agreement worked was because the Northern Ireland parties were around the table at all stages. There was a degree of buy-in from all communities because they were all involved.”
EU negotiator Maros Sefcovic was expected to brief officials from the bloc's 27 member states once a deal is reached. Diplomats said they had not yet received any details.
The meeting comes after intensive negotiations with the EU over the past few months, in which there was "positive, constructive progress”, according to Downing Street.
The UK and the EU have been at loggerheads over Northern Ireland — the only part of the UK that shares a border with an EU member, the Republic of Ireland — since Britain's exit from the trade bloc became final in 2020.
When the UK left the EU, 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.
Under the agreement, there are checks on some goods entering Northern Ireland from the rest of the UK.
That angers British unionist politicians, who insist that the new trade border undermines Northern Ireland's place in the UK.
Northern Ireland's power-sharing government has been non-functional since the Democratic Unionist party (DUP) walked out a year ago over the Protocol.
Speaking on Monday ahead of the meeting, prominent Brexiteer Jacob Rees-Mogg refused to say whether he supported the potential deal.
"There are two things we need to know. One is what the DUP thinks, because the protocol itself sets out in its first article that it is subsidiary to the Good Friday Belfast agreement. So if the DUP think it doesn't meet that test that will be very influential among Conservative MPs,” he told Good Morning Britain.
"And I am afraid with all EU deals, the devil is in the detail.”
He said from what he had heard, Mr Sunak had "done very well”.
"But I am not sure he has achieved the objective of getting the DUP back into power sharing, which is the fundamental point of it,” said Mr Rees-Mogg.
The latest announcement opens the door for a possible unveiling of new protocol terms during the German politician’s visit on Monday.
The commission’s online calendar says Ms von der Leyen’s meeting with Mr Sunak on Monday will take place in Windsor.
Had Saturday led to a breakthrough, Downing Street had reportedly been keen to call the deal the “Windsor Agreement”.
Mr Sunak on Saturday told The Sunday Times that he planned to work all weekend to revise the terms as he tries to keep hardline Conservative Brexiteers and the Democratic Unionist Party on side.
He said he was “giving it everything we’ve got” to finalise a fix for the protocol, a Brexit treaty negotiated by former prime minister Boris Johnson.
The protocol, signed by Mr Johnson in 2020, was designed to prevent a hard border with Ireland after Brexit, with Northern Ireland continuing to follow EU rules on goods to prevent checks being needed when crossing into the Republic.
But the trade barriers between Northern Ireland and Britain created by the treaty have caused Unionist tension, with Mr Sunak admitting they had “unbalanced” the Good Friday Agreement that helped to end the Troubles in the province.
DUP leader Jeffrey Donaldson has issued seven tests that Mr Sunak’s new pact will have to meet to win the party’s backing.
They include addressing the “democratic deficit” of Northern Ireland being subject to EU rules while not having a say in them.
Mr Raab, who is also the Justice Secretary, appeared to set out some of what has been agreed to so far negotiations.
The Leave campaigner said it was “right that there is a Northern Irish democratic check” on new rules the EU makes that apply to Belfast — a hint that Mr Sunak has tried to address the DUP’s concern over the democratic deficit.
He indicated that reports of red and green lanes to ease customs checks in Northern Ireland were correct.
“Those are the kind of things we have been pushing for,” he told Sky News.
Several reports have suggested that trusted traders would be able to send goods from Britain into Northern Ireland without checks, while goods destined for Ireland and the EU’s single market would go through red inspection lanes.
Mr Raab said the cut to trade bureaucracy would lead to a “substantial scaling back” of the role of the European Court of Justice, but he refused to rule out it having a say on future legal cases.
The ability of European judges to rule on disputes involving EU laws in Northern Ireland is a particular problem for Tory Eurosceptics.
Mark Francois, chairman of the European Research Group (ERG) of anti-EU Conservative MPs, told Sky that “less of a role” for the Luxembourg court was “not enough” of a concession.
Mr Sunak is expected to face anger within his party if he does not give Parliament a vote on any agreement with Brussels.
Mr Raab was reluctant to commit to giving MPs a vote.
The Justice Secretary, facing a number of questions on whether a vote would take place, told Sky: “I think, inevitably, Parliament will find a way to have its say.”
Mr Francois warned that any attempt by Downing Street to “bludgeon this through the House of Commons without a vote of any kind would be incredibly unwise”.
Mr Sunak is keen for his party to unite in any vote, to avoid him having to rely on Labour votes, with Keir Starmer’s party offering its backing if he fixes the major protocol obstacles.
But Mr Francois said that without the DUP’s support for any protocol deal, the revisions are “simply not going to fly”, leading to speculation that the ERG could also withhold voting in favour.