Theresa May is to publish fresh proposals for avoiding a hard border in Ireland in a last-ditch attempt to break the Brexit deadlock
The prime minister has told senior EU figures, as well as Irish Taoiseach Leo Varadkar, that the so-called "backstop" plans will be produced within the next fortnight.
The proposals – which would only be implemented if no withdrawal agreement can be reached – would keep Britain in a customs union with the EU beyond the post-Brexit transition period, which ends on 31 December, 2020.
It emerged on Wednesday night that the plan had been agreed at this week's meeting of May's Brexit war Cabinet, despite opposition from Boris Johnson and Michael Gove.
The prime minister has previously dismissed the EU's own backstop plans, which would effectively have kept Britain in the customs union and single market, as "unacceptable".
Following talks with EU Commission president Jean-Claude Juncker and EU Council president Donald Tusk in Sofia, Bulgaria, on Thursday, a Downing Street spokesman said: "The PM said the UK would be shortly putting forward its own backstop proposal in relation to customs."
On separate talks with Leo Varadkar, the spokesman said: "They agreed on their shared commitment to avoid a hard border between Ireland and Northern Ireland and on the need to continue talks on the way forward."
Speaking afterwards, Varadkar said: "I said to the prime minister that any move that helped to align all of the EU and the UK in terms of customs into the future would be beneficial.
"It would help solve some of the problems related to the border but not all of them. It would certainly help us continue to trade between Britain and Ireland much as we do now."
He added: "The prime minister gave me an insight into some new thinking the UK government as in relation to customs. Obviously, we'll see how that develops. We haven't been able to get any detail on that yet, but certainly any move on customs that brings the UK closer to the EU is to be welcomed.
"But I very much emphasised that resolving the issue of avoiding a hard border requires more than just customs."
The government has already published a white paper based on HMRC’s work setting out two possible options for customs after Brexit – a highly streamlined customs partnership and a new customs partnership. The first of these would seek to negotiate a continued waiver from the EU on the requirement to submit entry and exit summary declarations for goods being moved between the UK and the EU, while the second option could see the UK acting in partnership with the EU to operate a regime for imports that aligns precisely with the EU’s external customs border, even if goods enter the UK first.
However, the backstop will set out the arrangements to be applied if a wider customs deal cannot be reached. The Cabinet has been unable to agree which arrangement the government should choose, and European Union negotiators have warned that neither plan is likely to be acceptable.