Donald Tusk has said there are "no grounds for optimism" in relation to a Brexit deal ahead of a key summit of EU leaders.
Mr Tusk said the prime minister must put forward "concrete proposals on how to break the impasse", which centres on a disagreement over a customs backstop to preserve an open border Northern Ireland.
Earlier in the day, Ms May attempted to convince her Cabinet to back her Brexit plan, which could see the UK remain in the customs union indefinitely if no other method is found for avoiding a hard border between Northern Ireland and the Republic of Ireland.
The prime minister told ministers they must "stand together" but Downing Street said no decision was made on her controversial plan during a three-hour meeting.
Elsewhere, John Bercow reportedly told friends he would step down as House of Commons Speaker next summer. It came as he faced criticism from MPs over allegations of bullying, which he has denied, following the publication of a report into harassment in Parliament.
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