LONDON (AP) — The Latest on Britain's departure from the European Union (all times local):

5:15 p.m.

Ambassadors from the 27 European Union nations that are negotiating a Brexit deal with the United Kingdom are meeting late Sunday to assess progress in the talks. 

The surprise trip to Brussels by Britain's chief negotiator spurred speculation of a breakthrough in the difficult negotiations, a possibility reinforced by the call for the ambassadors to meet at EU headquarters. 

Three diplomats from different EU nations confirmed the ambassadors meeting is on, underscoring enough progress had been made to assess the situation. 

One diplomat said that if there are enough indications a deal can be outlined, the government of British Prime Minister Theresa May would meet to evaluate it on Monday. 

All three diplomats talked on condition of anonymity because the negotiations were still progressing.

— By Raf Casert in Brussels

1:50 p.m.

Britain's Brexit secretary is making a rushed visit to Brussels for surprise talks with the top European Union negotiator as Brexit talks accelerated ahead of a summit later this week.

Dominic Raab's office said in a statement that the unusual Sunday meeting with the EU's Michel Barnier was necessary.

The two are seeking a compromise position on the difficult Irish border question ahead of an EU summit that begins on Wednesday.

Raab's office said: "With several big issues still to resolve, including the Northern Ireland backstop, it was jointly agreed that face-to-face talks were necessary." Raab's office said.

Even if a deal is reached on Britain's divorce from the bloc, it's clear that British Prime Minister Theresa May will find it challenged at home.

Raab's predecessor, David Davis, wrote in the Sunday Times that May's plans for some continued ties with the EU even after Britain leaves the bloc is "completely unacceptable" and must be stopped by her ministers.

11:45 a.m.

Britain's former Brexit secretary is urging members of Prime Minister Theresa May's cabinet to rebel against her proposed deal with the European Union over the terms of Britain's departure from the bloc.

David Davis wrote in the Sunday Times that May's plans for some continued ties with the EU under her Chequers plan is "completely unacceptable" and must be stopped. The fellow Conservative party member said the time has come for ministers "to exert their collective authority" to shoot down May's plan.

May also faces obstacles from the Democratic Unionist Party in Northern Ireland, which has played a crucial role in propping up her minority government in Parliament.

DUP leader Arlene Foster remains opposed to any Brexit plan that would require any checks on goods traveling between Northern Ireland and Britain.