The EU's chief Brexit negotiator has said both sides in the talks needed to spell out how goods entering Northern Ireland from the rest of the UK would undergo EU conformity checks in the event of the disputed Irish backstop coming into play.
Michel Barnier said the EU and UK should "de-dramatise" the backstop by clarifying which controls were needed, where they should take place, and how they should be carried out.
According to a political agreement reached between the EU and UK last December, the so-called backstop would come into effect if other solutions to avoid a hard border did not work.
The backstop would see Northern Ireland remaining in the EU single market and customs union and if the UK remained outside both then goods entering Northern Ireland would have to undergo checks, leading to the accusation that that would require a border along the Irish Sea.
Speaking after several hours of negotiation with Brexit Secretary Dominic Raab, Mr Barnier repeated that there must be a legally operational backstop in the Withdrawal Agreement to be reached no later than November.
He drew attention to last December's Joint Report, in which British Prime Minister Theresa May agreed to a backstop if other solutions to avoiding a hard border were not found.
Mr Barnier told reporters: "We must find pragmatic solutions in line with the commitments made by Prime Minister May in December and March, and we must de-dramatise the issue and spell out which controls are needed, and where and how they should be done."
He said that both men would "take stock on this work" when they meet next week.
Mr Barnier added: "The negotiations are now entering the final stage. We have agreed that the EU and UK will negotiate continuously from now on."
He said the two would increase their meetings, and "move the negotiations forward".
Mr Barnier said both sides could find common ground between EU principles and the choices made by the UK.
"We are far more advanced in defining that common ground for foreign policy and security than for the economic relationship," he said.
"Our challenge for the coming weeks is to try and define an ambitious partnership between the UK and EU, a partnership that has no precedent.
"This partnership has to respect the single market and the foundations of the European project. If this is well understood, we can conclude negotiations successfully."
Mr Raab described the discussions as "positive" and "very useful on all three categories of issues".
The Brexit Secretary said he had reaffirmed the UK's commitment to the undertakings on Northern Ireland in the Joint Report, "but we must come up with solutions that are deliverable to the communities affected".
He added: "There are still some significant issues to overcome, yes on Northern Ireland, we both recognise that, and on the future relationship, but it's important to view the whole deal as a package.
"On our side we've shown the ambition, the energy and the pragmatism, and I know how committed Michel is to securing a deal, and if we have that ambition and pragmatism and that energy on both sides, I'm confident we can reach agreement in October."
Asked if the EU was being intransigent, as it had not changed its position in two years, Mr Barnier replied: "Why would we? How can you change principles on which European Union is based?
"The UK is leaving the European Union, it's not the other way around. The UK is leaving, it's their choice and we respect that choice, if we regret it.
"The EU is based on values, on rules. It's a whole ecosystem which is integrated with rules and laws, standards, of supervision, of certifcation, which the UK knows very well because we built it together."
Mr Barnier said that the Withdrawal Agreement would have to be reached "not much later than" the beginning of November if there was to be time for both the House of Commons and the European Parliament to ratify the deal.
