Britain and Ireland clashed over Brexit on Friday with Dublin saying it was not ready to allow talks to move on to trade issues next month and London ruling out the much longer transitional period preferred by its neighbour.
The border between EU-member Ireland and Northern Ireland, which will be the UK's only land frontier with the bloc after its departure, is one of three issues Brussels wants broadly solved before it decides in December whether to move the talks onto a second phase about trade, as Britain wants.
Meeting in Dublin, Britain's Foreign Secretary Boris Johnson and his Irish counterpart Simon Coveney struck an amicable tone but remained far apart on several key aspects.
"Yes we all want to move onto phase two of the Brexit negotiations but we are not in a place right now that allows us to do that," Coveney said. "We have very serious issues, particularly around the border, that need more clarity."
He said Ireland's preference was that Britain as a whole would share the same regulations as the EU post-Brexit but if that was not possible, then London effectively needed to commit to allowing a tailor-made solution for Northern Ireland.
"In the absence of that, from an Irish perspective, there is a sense of jumping into the dark," Coveney said.
Speaking before a meeting with his counterpart on the sidelines of a European Union summit in Sweden, Irish Prime Minister Leo Varadkar said Dublin would need those assurances written into the conclusions of phase one.
"What we want to take off the table before we even talk about trade is any idea that there would be a physical border," he told reporters. "Once those parameters are set, then we'd be happy to move onto phase two, provided the other issues are resolved as well."
Johnson said moving the talks onto the next stage would help to resolve the border issue as many of the questions around it were bound up with Britain's future customs arrangement with the European Union.
"The British government has absolutely no interest whatever in seeing any kind of hard border..," he said.
Johnson added that he understood why Ireland wants a four to five-year post-Brexit transition period for Britain to allow businesses in Ireland time to adjust to any new arrangements, but said this was possible within a much tighter timescale.
"I think it's possible to do that in a much shorter timescale... Now is the time to make haste (on moving onto stage two of Brexit talks) and perhaps we don't need to wait quite so long to give business final certainty about how it's all going to work."