Only two days ahead of a summit once seen as the moment when Britain and the European Union would have to reach a Brexit deal, both sides are still refusing to blink over the question of the Irish border.
A flurry of diplomatic meetings over the weekend had raised hopes for an agreement on Britain's divorce from the bloc. But they were disappointed by the issue that has dogged the talks for months — how to ensure that no hard border is created between the EU's Ireland and Britain's Northern Ireland once Brexit happens on March 29.
The EU has proposed keeping Northern Ireland in a customs union to avoid a hard border between it and Ireland. Yet fears are that such a border could revive tensions between Northern Ireland's pro-Irish Catholic community and its pro-U.K. Protestant one. Decades ago, over 3,700 people were killed in Northern Ireland amid 30 years of violence between the two groups and Britain, which ended with a 1998 peace deal.
Britain says it will only accept that EU Brexit plan if it is temporary and does not hive Northern Ireland off permanently from the rest of the U.K. in terms of customs arrangements.
British Prime Minister Theresa May's spokesman James Slack said Monday that negotiations are stuck because the EU "continues to insist on the possibility of a customs border down the Irish Sea." Britain feels that move will effectively split up the U.K., which is made up of England, Scotland, Wales and Northern Ireland.
The acrimony means it is almost impossible that EU leaders will reach a deal at their summit, which begins Wednesday. The British and EU parliaments need to approve any deal, a process that could take months ahead of Britain's official exit on March 29.
German Chancellor Angela Merkel, perhaps the strongest voice in the EU, insisted that May should not count on the EU to blink first for fear of losing valuable business. Merkel said Germany wants an orderly departure of Britain from the bloc "but not at any price."
EU negotiators and leaders have said that Britain should not seek to cherry-pick the best parts of staying in the EU and leave the tough parts out in its withdrawal agreement and future relations.
"We must not allow our single market, which is really our competitive advantage, to be destroyed by such a withdrawal," Merkel said told Germany's main exporters' association. "And if it doesn't work out this week, we must continue negotiating, that is clear — but time is pressing."
Britain refuses to be pinned down on a date for a fixed Brexit deal.
"Whether we do (it) this week or not, who knows?" British Foreign Secretary Jeremy Hunt told reporters in Luxembourg, where EU foreign ministers are meeting.
If Britain leaves the EU without an agreement on future relations, there could be chaos — tariffs would go up on trade, airlines could no longer have permits to fly between the two regions, and freight could be lined up for miles at border crossings as customs checks are restored overnight.
To avoid this, the prospect of an extra EU meeting in November was raised, but only if there was decisive progress this week.
Irish Foreign Minister Simon Coveney admitted to being "frustrated" by the delay, saying that apart from Britain, Ireland is the country with most to lose from Brexit.
Coveney suggested that May is reneging on part of Britain's commitment to ensure that no hard border involving lengthy customs checks and controls emerges on the Irish island.
He said Britain agreed in December and again in March that an unpopular EU "backstop" guarantee would remain in place until a better solution is found, but now appears to only want it used for a limited time.
"A backstop cannot be time-limited. That's new. It hasn't been there before," he said. "Nobody wants to ever trigger the backstop, but it needs to be there as an insurance mechanism to calm nerves that we're not going to see physical border infrastructure re-emerging."
Britain denied it is reneging on its December commitment to avoid a hard Irish border.
Spanish Foreign Minister Josep Borrell, meanwhile, said he foresees no Brexit problems between Britain and Spain over Gibraltar, the British territory on the border of Spain.
"It's not a rock in the way," Borrell said, referring to Gibraltar's nickname. He added the Irish border problem is "more difficult to solve than Gibraltar."
May is under intense pressure from her Conservative Party and its parliamentary allies not to give any more ground in Brexit negotiations, especially on the border issue. May's political allies in Northern Ireland, the Democratic Unionist Party, stand ready to scuttle a Brexit deal over the Irish border issue.
DUP Brexit spokesman Sammy Wilson said "it is probably inevitable that we will end up with a no-deal scenario" over Brexit because he felt was no Brexit agreement that would be accepted by Britain's Parliament.