Theresa May has been meeting Brexit Secretary David Davis amid tensions over the UK’s Brexit “backstop” plan.
The proposal would see the UK match EU trade tariffs temporarily in order to avoid a hard Irish border post-Brexit.
No 10 had been expected to publish the “temporary customs arrangement”, but faced resistance from Mr Davis because there had been no end date included.
Brexiteers are concerned that without a fixed end date the arrangement could continue indefinitely.
The UK is due to leave the EU in March 2019, and the government is trying to make progress before a crucial meeting of EU leaders later this month.
BBC political editor Laura Kuenssberg said Mr Davis had “pushed back very hard” against the proposals on Wednesday.
She said the prime minister and Mr Davis had talks lasting for about an hour on Thursday morning – but no conclusion was reached and the two then held a second meeting ahead of the scheduled early afternoon Cabinet Brexit committee meeting.
A source close to Mr Davis told the BBC after the second meeting that the “the paper has been amended and now expresses in much more detail the time-limited nature of our proposal”.
No 10 said the PM had also held meetings earlier with Foreign Secretary Boris Johnson and International Trade Secretary Liam Fox.
The PM’s official spokesman described the meetings as “constructive” and – with speculation Mr Davis might quit over the issue – was asked if anyone had threatened to resign. He replied: “No.”
The spokesman said the “backstop” plan would be published “shortly” with one source telling the BBC there would be “more clarity” on the time limit aspect.
What is the customs ‘backstop’ issue?
The UK has said it will leave the EU’s customs union, which allows trade within the EU without any tariffs or many border checks.
The UK and the EU are yet to agree how trade in goods will operate after Brexit – but they have said that a “backstop” option is needed in case no deal is done, or the technology is not ready in time, to avoid the return of a hard border between Northern Ireland and the Republic of Ireland.
The UK has said that the EU’s initial “backstop” proposal – effectively keeping Northern Ireland in the customs union – would create what amounted to a border between Northern Ireland and the rest of the UK and was not acceptable.
Instead, the UK is proposing a backup plan which would see the whole of the UK temporarily aligned with the EU’s customs union after December 2020 – when the 21-month post-Brexit transition period ends.
The plan, which Theresa May has said would only apply in a “limited set of circumstances”, would see the UK match EU tariffs in order to avoid border checks.
Mr Davis is said to believe that the proposals should not only be time-limited but should also specify an end date.
He told a press conference on Wednesday that he “expected” there to be a time limit in the signed-off version of the plan.
Speaking in London, he said the details had yet to be approved and that he believed Thursday’s meeting of the cabinet’s Brexit sub-committee would be “decisive”.
What are Brexiteers worried about?
Former Brexit Minister David Jones explained why Eurosceptic MPs are concerned about the plans.
With the EU sceptical about the two options the UK has suggested to replace its membership of the customs union – and government ministers yet to agree which one to pursue – the backstop is “rapidly becoming the only option on the table”, he told BBC Radio 4’s Today programme – “so it must be got right”.
Mr Jones said the arrangement as set out would be “damaging to the country”.
“It would tie us effectively into the the EU’s customs arrangement for an indefinite period” he said, adding that “time-limited” and “indefinite” do not go together.
It would prevent the UK from having its own independent trade policy, he said – customs union members are not allowed to strike their own international trade deals.
It would also mean the UK was still under the jurisdiction of the European Court of Justice, which would be unacceptable to most Conservative MPs, he added.
Asked about reports Mr Davis could resign over the row, Mr Jones said the Brexit secretary would be a “huge loss to the government”.
“I think that we need to make sure that David Davis stays at the negotiating table,” he added.
Brexiteer Iain Duncan Smith on David Davis’s position
The view from the EU
In Brussels, the view is that the UK government is “still talking to itself”, said BBC Europe editor Katya Adler. “While it’s doing that it’s not coming here with a unified position.”
The EU side is “paying very close attention to what’s going on”, with doubts over whether the UK’s first choice solutions for solving the customs problem will be ready in time, she added.
BBC Brussels reporter Adam Fleming says the EU will apply a series of tests to any proposal about customs from the UK.
He lists them as: “Will it be temporary and what does it say about an end point? How far does it go to solve the issue of the Irish border? How does it interact with the EU’s own customs policy, for example when it comes to preventing fraud or dealing with imports of – say – subsidised Chinese steel that break international trade law?
“Does it require the EU to change its rules, and what happens when new ones are introduced? And what about product standards, something else that gets checked at the border along with customs.”