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?" the former Polish premier said.
"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.
"Our optimism should still be extremely cautious but we have good reason to talk about it," Tusk said shortly before the summit opens at 1300 GMT.
CAN MAY DELIVER?
In Brussels, security has been stepped up after Tuesday's bombing at one of the city's main rail stations by an Islamic State sympathizer, following attacks in Britain and France.
Macron won office as a committed European and has joined forces with German Chancellor Angela Merkel pledging to put the EU back on track to deliver prosperity and security after years of austerity and crisis.
But talks on issues including post-Brexit defence plans risk being overshadowed by concerns that a disastrous election has left May so enfeebled that Brexit negotiations will be hampered.
"There is an enormous insecurity among the Europeans: how long will she last? Has she got the majority to deliver?" a senior EU official said.
Over dinner, May is expected to fill in some of the blanks for the other EU leaders on Brexit.
It will be their first meeting since her Conservative party unexpectedly lost its majority in a June 8 election, leaving her in charge of a so-called "zombie government".
Britain's shock referendum vote to leave the EU was a year ago on Friday, and the country remains in a dark national mood after a string of terror attacks and a deadly tower block blaze.
CITIZENS' RIGHTS A KEY ISSUE
"The PM will give an update to the other member states on the UK's Brexit plans following the beginning of the negotiations this week," a Downing Street spokesman said.
During the dinner May will "outline some principles of the UK's paper on citizens rights which will be published at the beginning of next week," the spokesman said.
The EU has made a priority of the rights of three million European citizens living in Britain, plus a million Britons resident in Europe.
At the first formal Brexit negotiations Monday, Britain accepted the EU's timetable that the exit bill, citizens' rights and the Northern Ireland border be settled before its request for a free trade deal be considered.
After her comments, May will leave the room for the remaining 27 EU member states to discuss what she has told them, and the future relocation of key EU agencies from London.
Macron and Merkel are expected to recommend another six-month rollover of tough economic sanctions imposed in 2014 against Russia over the conflict in eastern Ukraine, which has claimed 10,000 lives.
Tusk and European Commission head Jean-Claude Juncker are also expected to report on recent meetings with US President Donald Trump.
Trump's "America First" approach and dismissive remarks about the EU and NATO have and bolstered calls for the European Union to take on an increased defence role, while his decision to pull out of the Paris climate pact infuriated Europe.