European Union leaders in a rare show of unity on Brexit demands

European Union leaders endorsed a stiff set of divorce terms for Britain at a summit Saturday, rejoicing in a rare show of unity in adversity but well aware that may start to fray once negotiations begin.

Meeting for the first time since British Prime Minister Theresa May formally triggered a two-year countdown to Brexit in late March, the 27 other EU leaders took just a minute as they sat down to lunch in Brussels to approve 8 pages of negotiating guidelines hammered out by their diplomats over the past month.

"Guidelines adopted unanimously. EU27 firm and fair political mandate for the Brexit talks is ready," summit chair Donald Tusk tweeted. Leaders applauded, officials said, after formally adopting unmodified the text drafted by their aides.

Those will bind Michel Barnier, their chief negotiator, to seek a deal that secures the rights of 3 million EU expats living in Britain, ensure London pays tens of billions of euros Brussels thinks it will be owed and avoids destabilising peace by creating a hard EU-UK border across the island of Ireland.

"We are ready," Barnier said. "We are together."

They also rule out discussing the free trade deal May wants until they see progress on agreeing those key withdrawal terms.

"Before discussing the future, we have to sort out our past," Tusk said in comments echoed by German Chancellor Angela Merkel, who said "substantive issues" must first be settled.

In a mark of how last year's Brexit vote has called into question the unity of the United Kingdom itself, leaders will also offer Irish Prime Minister Enda Kenny a pledge that if Northern Ireland, which voted against Brexit, ever unites with his country, it will automatically be in the EU.

The leaders may spend more time in discussions, including with Barnier, on what criteria they may use to judge, come the autumn, whether he has made sufficient progress to warrant a start on trade talks.