"Cabinet Ministers have been invited to read documentation ahead of that meeting", the spokesperson said in a statement on Tuesday.
May's government is braced for possible resignations.
The Irish government has dismissed reports of a breakthrough in the Brexit negotiations as "speculation".
British Prime Minister Theresa May is gearing up for a tough fight at home, as she prepares to reveal a draft Brexit agreement to her cabinet on Wednesday.
Earlier this month, Irish Prime Minister Leo Varadkar said Brexit has "undermined" the landmark Good Friday Agreement, which in 1998 ended decades of violence in Northern Ireland.
The backstop will take the form of a temporary UK-wide customs agreement, with specific provisions for Northern Ireland which are more in dept regarding customs and single market rules alignment than for the rest of Britain.
Brexit will pitch the world's fifth largest economy into the unknown and many fear it will serve to divide the West as it grapples with both the unconventional presidency of Donald Trump and growing assertiveness from Russian Federation and China.
Brexiteers MPs, both in and out of the cabinet, have repeatedly raised their opposition to the United Kingdom signing a backstop arrangement that will keep the country in the customs union. The UK would also have to continue following numerous European Union rules in areas like the environment, employee protections and state aid.
Mr Rees-Mogg told BBC Newsnight it was "not what we were promised", saying he could find it "very hard to carry on supporting" the prime minister.
"We want to be clear that this would be wholly unacceptable", it said. Labour, too, are threatening to vote it down if it doesn't meet their six tests.
In a sign that Brexit talks could go down to the wire, European Union sources told Reuters they want clarity from London by the end of Wednesday at the latest if there is to be a summit this month to approve a Brexit deal. European Union ambassadors are set to meet on Wednesday to discuss the next steps in the Brexit process.
The news saw the British pound shoot up in value to 1.304 dollars from 1.285 on Tuesday at 2200 GMT.
5 people found dead in vehicles torched by fire
Butte County Sheriff's Office said an evacuation ordered had been issued for the small communities of Stirling City and Inskip. Evacuation orders included the entire city of Malibu , which is home to 13,000, among them some of Hollywood's biggest stars .
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".
"We need to work together as a Cabinet to do that".
Meanwhile, pro-EU Conservative MP Justine Greening said the agreement would leave the United Kingdom with less influence and undermine its credibility. She told the BBC: "I don't think something that trapped the United Kingdom in any arrangement against our will would be sellable to members of Parliament".
There has been no official confirmation from either Downing Street or Brussels. If more high profile figures quit, her life becomes complicated again.
Brexit Secretary Dominic Raab said on Tuesday he was confident of progress in talks, though he gave no further details.
"There is huge opposition to that too and one of the reasons for that is the idea that this place, charged and paid to deal with this problem can't, and hands this prickly problem back to the people, that is a very bad look and one I know which colleagues will want to avoid".
The DUP's Nigel Dodds said the party "couldn't possibly vote for" the deal.
May described the negotiations as immensely hard and said there would not be an agreement at any cost.
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Eurosceptic opponents promised to scuttle it in parliament, where, ever since losing a snap 2017 election, May has had to rely on the support of 10 Northern Irish lawmakers for her majority. "This deal will dictate the course for our country for generations to come, and it must be put to the people for their approval or rejection".
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