Former Conservative leader and Brexit supporter Iain Duncan Smith warned the prime minister she should "listen very carefully" to the DUP, which he said echoed many Tory concerns. However, the British government would be able to point to criteria under which the arrangement would be terminated, fulfilling the British desire for it to appear to be a temporary arrangement.
The nature of those criteria, and additional language to be used about the future deal, required by the United Kingdom to assuage concerns about the ultimate need for such a backstop solution to avoid a hard border on the island of Ireland, are still open to debate.
Earlier on Thursday, May told Northern Ireland journalists that Irish border talks would likely continue until November.
Instead she proposed Britain as a whole stay temporarily aligned with the EU's customs union until a wider trade deal is agreed.More news: Action Needed Now in Climate Crisis
Those present included Jeremy Hunt, the foreign secretary, David Lidington, the Cabinet Office minister, Sajid Javid, the home secretary, and Michael Gove, the environment secretary. "There are big issues still to resolve".
He referred further questions to Barnier, who was due to make a speech to European business leaders later in the day.
The agreement will also see Northern Ireland remain within the single market in a bid to avoid a hard border on the island of Ireland, should both sides fail to secure a trade deal after the transition period.
One official close to Brexit talks said May never brings the cabinet together to tell them recent developments and so "it feels to me like the deal is practically done", the FT quoted the official as saying.More news: Dow plummets 800 points, biggest drop in 8 months
Arlene Foster's party have threatened to vote down the upcoming Budget if Mrs May pushes on with plans to accept a number of regulatory checks between Northern Ireland and Great Britain.
The European Union is doing all it can to ensure checks on goods moving across Northern Ireland's borders would be made "in the least intrusive way possible", for example on ferries, at ports or in factories of origin, he said.
"Brussels wants Northern Ireland to have access to the EU single market and trade within the rules set by the EU under the European Courts of Justice", she said.
Whitehall sources said before the meeting that they expected that key members of the cabinet would also discuss how to handle the DUP. "Michel Barnier and his team are working day and night to reach a deal, but we are not there yet", he said.More news: Manchester United's Paul Pogba