Northern Ireland’s Democratic Unionist Party dramatically rejected the accord, which would see their British-ruled province remain under EU customs and Value Added Tax rules.

BRUSSELS, Belgium (AFP) — Britain’s efforts to agree an amicable divorce from the European Union (EU) were hanging by a thread Thursday as leaders headed to Brussels for the latest crunch summit.

EU and UK negotiators had worked late into the night on a compromise withdrawal deal that Prime Minister Boris Johnson hoped to present to his counterparts.

But, as dawn broke over Brussels, Northern Ireland’s Democratic Unionist Party dramatically rejected the accord, which would see their British-ruled province remain under EU customs and Value Added Tax rules.

It was not immediately clear if this meant that Johnson’s British government would also have to back away from the draft text, but it greatly complicates his chances of getting it through parliament.

And EU leaders will be loath to approve another withdrawal agreement only to see it rejected in London, as happened with the last Brexit deal.

“As things stand, we could not support what is being suggested on customs and consent issues, and there is a lack of clarity on VAT,” the DUP said.

“We will continue to work with the Government to try and get a sensible deal that works for Northern Ireland and protects the economic and constitutional integrity of the United Kingdom.”

In Brussels, EU officials were expecting more contacts with British representatives in the morning before Johnson and the other 27 EU leaders arrive in the early afternoon for the two-day European Council summit.

Before the DUP statement there had been guarded optimism that this time, just two weeks before Britain is due to quit the bloc, the groundwork was there for a deal to avoid calamitous economic disruption.

“An agreement appears within reach but it is not guaranteed,” French deputy foreign minister Jean-Baptiste Lemoyne said. “We’re hoping for a deal and if it can come in the coming hours, that would be perfect.”