Britain and the European Union failed on Wednesday to agree any solutions to ease post-Brexit trade with Northern Ireland, in a standoff that is not only deepening mistrust between the two sides but could also cloud a weekend international summit.
Since Britain completed tortuous exit from the EU late last year, its relations with Brussels have soured further, with both sides accusing each other of bad faith over a part of their trade deal that covers goods movements to Northern Ireland.
The row has been dubbed the "sausage war" by British media because it affects the movement of chilled meats from Britain to Northern Ireland.
Prime Minister Boris Johnson wants a summit of the world's seven largest advanced economies this weekend at a seaside village in southwestern England to showcase what he calls "global Britain".
But he could receive a warning from US President Joe Biden, who, according to the Times newspaper, will tell London to respect a deal with the EU that was designed to protect a 23-year-old peace settlement in Northern Ireland.
In the latest round of talks, British Brexit minister David Frost, who is also expected to attend the summit, met European Commission Vice President Maros Sefcovic in London to try to resolve the differences over the Northern Ireland protocol.
"We had some pretty frank and honest discussions ... There weren't any breakthroughs. There aren't any breakdowns either, and we are going to carry on talking," Frost told reporters.
"What we now need to do is very urgently find some solutions."
In a statement, the government said there had been no substantive progress on the main issue of the movement of some foodstuffs.
"There is an urgent need for further discussions in order to make real progress, particularly to avoid disruption to critical supplies such as medicines," it said.
Preserving the delicate peace in Northern Ireland without allowing the United Kingdom a back door into the European Union's single market through the 310-mile (500 km) Irish land border was one of the trickiest issues of the Brexit divorce.
The result was the Northern Ireland protocol, which essentially kept the British-ruled province in the EU's customs union and adhering to many of the rules of its single market -- both of which the rest of Britain has left.
Brussels accuses London of failing to implement agreed checks on some goods moving from Britain to Northern Ireland, and has started legal action over London's unilateral extension of a "no-checks" grace period.
London says it has no choice because some of the checks hamper supplies to Northern Irish supermarkets. It has also pointed to rising tensions among pro-British unionists in the province, who say the protocol undermines the 1998 peace agreement by loosening their ties to Britain.
"We've put forward some solutions to the EU," housing minister Robert Jenrick told Sky News. "It can't be right that ... sausages can't travel from Bangor in Wales to Bangor in Northern Ireland."