UK and EU officials have agreed on the draft text of a Brexit agreement after months of negotiations in Brussels.
A Cabinet source told the BBC that the document has been agreed at a technical level by officials from both sides after intensive discussions this week.
A special Cabinet meeting will be held at 14:00 GMT on Wednesday as Theresa May seeks ministers' backing.
The PM is meeting ministers in Downing Street for one-to-one talks as they are given sight of the draft agreement.
The
- but analysts warned it could be short-lived, with the cabinet and Parliament yet to agree to the plans.
The EU said it would "take stock" on Wednesday, and the Irish government said negotiations were "ongoing and have not concluded".
Leading Brexiteers, such as Boris Johnson and Jacob Rees-Mogg, have urged cabinet ministers to reject the draft agreement, which they claim would keep the UK under EU control, based upon leaked versions of the text.
Northern Ireland's Democratic Unionist Party, which gives Theresa May vital support in key votes, said it would be a "very, very hard sell".
But Conservative Chief Whip Julian Smith said he was "confident" it would get through Parliament.
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.
The draft agreement also 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".
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 text that's taken months of officials' blood, sweat and tears has been agreed on, 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.
Johnson said the plan 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" and that he would vote against it.
Rees-Mogg warned of the UK becoming a "vassal state" with Northern Ireland "being ruled from Dublin".
Labour leader Jeremy Corbyn said "given the shambolic nature of the negotiations, this is unlikely to be a good deal for the country".
Failure to deliver
Both the UK and EU want to schedule a special summit of European leaders at the end of November to sign off the reportedly 500-page withdrawal deal and the much shorter outline declaration of their future relationship.
Brussels has insisted it would only agree to put the wheels in motion for the summit if an agreement can be reached on the issue of the Irish border.
Ambassadors from the remaining 27 EU states will meet in Brussels on Wednesday.
If a deal is agreed with the EU, May then needs to persuade her party - and the rest of Parliament - to support it in a key Commons vote.
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 Irish 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".