UK and EU officials have agreed the draft text of a Brexit agreement in a significant breakthrough for the talks.
A cabinet source told the BBC that the document has been agreed at a technical level by officials from both sides after intensive talks this week.
A special cabinet meeting will be held at 14:00 GMT on Wednesday as Theresa May seeks ministers’ backing.
Every minister is being asked to see the prime minister for one-to-one talks on Tuesday evening.
Health Secretary Matt Hancock, Transport Secretary Chris Grayling and Chief Whip Julian Smith are among those who have been seen entering Downing Street.
Leading Brexiteers, such as Boris Johnson and Jacob Rees-Mogg, have urged the cabinet to reject the draft agreement – which includes commitments over citizens’ rights after Brexit, a proposed 21-month transition period after the UK’s departure on 29 March 2019 and details of the so-called £39bn “divorce bill”.
The future of the border between Northern Ireland and the Republic of Ireland has been the last major outstanding issue to be settled amid disagreements over how to guarantee that there will not be physical checks reintroduced after Brexit.
- Kuenssberg: Agreement is in Downing Street’s grasp
- Live: Latest in Brexit negotiations
- A brief guide to where we are with Brexit
Cabinet ministers were briefed on the state of the negotiations earlier on Tuesday, when they were told a “small number of outstanding issues” remained to be sorted.
No 10 said ministers were now being called to a special meeting to “consider the draft agreement the negotiating teams have reached in Brussels, and to decide on next steps”.
Before they do so, they will be able to read relevant “documentation”.
The BBC’s chief political correspondent Vicki Young said some ministers had “deep concerns” about the the shape of the likely agreement, which critics say could leave the UK trapped in a customs agreement with the EU.
She said they would have to decide whether they could support it, and if not, whether to resign from cabinet.
Cranking into action
BBC political editor Laura Kuenssberg
Agreement is finally in Number 10’s grasp.
The text that’s taken months of officials’ blood, sweat and tears has been agreed, at least at a technical level.
Now a paper’s being drafted to present to the Cabinet tomorrow ready for the government’s hoped-for next step – political approval from Theresa May’s team, even though many of them have deep reservations.
Remember in the last 24 hours some of them have been warning privately that what’s on the table is just not acceptable, and will never get through Parliament. Some even believe the prime minister ought to walk away.
But the government machine is now cranking into action. With a text ready, their long-planned rollout can begin.
Leading Brexiteers have already condemned the draft agreement, Boris Johnson saying it would see the UK remain in the customs union and “large parts” of the single market.
He told the BBC it was “utterly unacceptable to anyone who believes in democracy”. “Am I going to vote against it. The answer is yes,” he added.
In another development, ambassadors from the remaining 27 EU states will meet in Brussels on Wednesday.
Both the UK and EU want to schedule a special summit of European leaders at the end of November to sign off the withdrawal deal and an outline declaration of their future relationship ahead of the UK’s exit on 29 March.
‘Failure to deliver’
Brussels has insisted it would only agree to put the wheels in motion for the summit if agreement can be reached on the issue of the Irish border.
If a deal is agreed with the EU, Mrs May then needs to persuade her party – and the rest of Parliament – to support it in a key Commons vote.
Conservative Brexiteer Jacob Rees-Mogg said if details of the text reported by Irish broadcaster RTE were true, the UK would become a “vassal state” with Northern Ireland “being ruled from Dublin”.
Such an agreement “failed to deliver on Brexit” and the cabinet should reject it, he told the BBC.
- Reality Check: When is the crunch time?
- Q&A: The Irish border backstop
- Bisto owner plans Brexit stockpile
“I think what we know of this deal is deeply unsatisfactory,” he said. “There seems to be growing opposition to these very poor proposals.”
Meanwhile, following pressure from all sides of the Commons, ministers have agreed to provide MPs with a legal assessment of the implications for the UK of the backstop and other controversial aspects of any deal.
Cabinet Office minister David Lidington said Attorney General Geoffrey Cox would make a statement to MPs and take questions ahead of the final vote on any Brexit deal.
MPs, he said, would get to see “a full reasoned position statement laying out the government’s both political and also legal position on the proposed withdrawal agreement”.
The DUP’s Westminster leader Nigel Dodds said he was pleased Parliament had “asserted its will” as it was imperative that all parties to the deal were clear in what way and for how long it would “legally bind” the UK.
Brexit: UK and EU ‘agree text’ of draft withdrawal agreement}