BRUSELLS - European Council President Donald Tusk on Thursday said Brexit could be reversed as leaders gathered for a Brussels summit amid growing confidence in a future without Britain.

Embattled Prime Minister Theresa May will make EU leaders an offer on the rights of expats after Britain's withdrawal as she tries to convince them she still has a grip after her election meltdown.

But Tusk, who has repeatedly said Brexit benefits no one, especially not Britain, channeled former Beatles John Lennon as he became the latest in a series of EU leaders to suggest it was not too late to change tack.

"Some of my British friends have asked me whether Brexit could be reversed, and whether I could imagine an outcome where the UK stays part of the European Union," Tusk told reporters.

"I told them that in fact the European Union was built on dreams that seemed impossible to achieve, so who knows? "You may say I am a dreamer, but I am not the only one," he added with a broad smile, quoting Lennon's iconic song "Imagine." Newly-elected French President Emmanuel Macron and German Finance Minister Wolfgang Schaeuble both said last week that the "door was open" for Britain to remain in the EU.

Tusk insisted the remaining 27 members had a renewed sense of optimism about the bloc's future after years of crisis and mounting anti-EU sentiment culminating in the Brexit vote.

Despite it being his 80th summit as premier or EU head, "never before have I had such a strong belief that things are going in a better direction," he said.