The UK's Brexit minister Dominic Raab has said he is confident that a workable backstop could be found to resolve the issue of the border after Brexit, but said any such backstop needed to be limited in time.
Mr Raab said the UK and the European Union had agreed on matters related to citizens' rights after Brexit and on a financial settlement and were stepping up efforts to ensure there was no hard border.
"With pragmatism on both sides I am confident we can find away to resolve it into a workable solution and that will be easier to achieve if the backstop, if it were to be exercised at all, could only be for a time-limited period before the future arrangements become operational," he told a news conference.
Mr Raab said there could be no deal until the whole deal was done.
The EU's chief Brexit negotiator Michel Barnier said it was clear to the bloc that what the UK had agreed to had been definitively agreed.
He also made clear that Brussels still has reservations about Mrs May's proposed backstop arrangement for the border, which would see the whole UK matching EU trade tariffs for a period if a trade deal is not reached by 2021.
"We have no objection in principle to this but we have doubts that it can be done without putting at risk the integrity of our customs union or commercial policy our regulatory policy," said Mr Barnier.
Mr Raab and Mr Barnier held face-to-face talks in Brussels today.
Their meeting comes at the end of the current round of talks, and as both sides step up plans to cope with a possible collapse in negotiations leading to a hard Brexit.
The European Commission has told member states and firms operating in the EU to step up their own preparations for a "cliff edge" Brexit.
Mr Barnier has blown a hole in British Prime Minister Theresa May's Chequers plan by flatly rejected a key element of her proposals for future relations following the UK's withdrawal.
Central to Mrs May’s plan, set out in a White Paper a fortnight ago, is a "facilitated customs arrangement" under which tariffs charged at the border would be passed on to either the British or EU authorities depending on the destination of imported goods.
Appearing alongside Mr Raab following their second round of talks in Brussels, Mr Barnier left no doubt that this was not acceptable to the EU.
"The EU cannot and the EU will not delegate the application of its customs policy and rules and VAT and excises duty collection to a non-member who would not be subject to the EU's governance structures," he said.
Any customs arrangement or union "must respect this principle".
Mr Raab signalled that he is looking for compromise from Brussels in response to Mrs May's White Paper, noting that the EU was able to take an "innovative" approach "when the political will has been there".
He appeared to be making an attempt to separate the thorny issue of the border from the rest of the Withdrawal Agreement which is due to be settled by October, repeatedly referring to a "protocol" on Northern Ireland.
Mr Barnier bluntly rebuffed Mr Raab's suggestion that the UK might tear up its promise to pay a £39 billion "divorce bill" unless it got a good deal on future trade.
Mr Barnier told him that, while the commitment to a financial settlement made by Mrs May in December was not yet in its final legal form, the 27 remaining EU members and European Parliament regard it as "agreed for good".