"The EU27 has agreed that it will accept the UK's request for a Brexit flextension until 31 January 2020," Tusk said of the idea of a "flexible extension", which means Britain could go earlier if its fractious parliament ratifies the divorce bill.

The bloc now awaits an approval from London. Once that is in, a 24-hour countdown will start when member states can still object or else the decision will have been taken.

"This will allow for the decision to be formally adopted tomorrow," an EU diplomat said.

An EU official warned, however, it might take as long as Wednesday, just a day before Britain would otherwise be due to leave the bloc on its current Oct. 31 deadline.