Britain's Brexit Secretary Dominic Raab has said London does not have a solution to the Irish border question.
He told the European Union Select Committee in the House of Lords: "I don't have the solution to give you yet."
Referring to a previously published joint report from the European Union and the UK, he said: "We are committed on both sides to giving effect to the joint report and I would also want to affirm our confidence that the proposals that we set out for the future relationship provide a good basis on which to resolve this issue on a sustainable basis".
Asked about potential border checks and what form they make take, Mr Raab said: "One of the frustrations from the UK side has been with the legalism of the EU versus the impact it would have on communities on the ground - both north of the border but also in fairness south of the border.
"So I think that ought to be the starting and indeed the end point of the 'check' as to whether we got a viable, workable solution.
"It's about the impact it would have."
'New solutions' on the backstop
"We've made clear we would see no return to the hard border or additional infrastructure".
"I think in fairness, (EU chief negotiator) Michel Barnier has also confirmed that he's open to new solutions on the backstop.
"And he said that the backstop that we eventually agree is not necessarily going to be the one that the Commission came up with - and he's acknowledged that it can be amended and improved.
"So there's a lot of technical work still underway.
"I'm not going to either give you a solution today, unfortunately, or give away the integrity of the negotiation room.
"But what I can say is that we're both committed and there's a of interesting technical, innovative work going on to make sure we resolve it".
But he added: "We're not going to see a customs border drawn down the Irish Sea, we're not going to do anything which would imperil the Belfast Agreement - and we want to make sure in a positive sense that the solution works for the communities on both sides".
Mr Barnier has previously warned that Britain will crash out of the EU without a deal, unless a solution can be found on the Irish border.