BRUSSELS -- European Union leaders vowed Saturday to stand shoulder to shoulder behind their negotiating team during the divorce proceedings with the United Kingdom and warned that demands from British Prime Minister Theresa May will be dealt with "firmly."
"Unity in action," European Commission President Jean-Claude Juncker said on Twitter as he announced that the 27 EU governments rubber-stamped the negotiating strategy in less than 15 minutes at a summit in Brussels.
The EU leaders in Brussels finalized the cornerstones of their negotiating a month after the British leader triggered two years of exit talks March 29. The negotiations themselves are to open shortly after Britain holds an early election June 8.
"We now have unanimous support from all the 27 member states and the EU institutions, giving us a strong political mandate for these negotiations" under chief negotiator Michel Barnier, European Council President Donald Tusk said.
Tusk said there can't be any discussions on the future relationship between the EU and Britain until there has been major headway on key issues.
"We must first achieve sufficient progress on citizens' rights, finances and the border issue in Ireland. It is too early to speculate on when this might happen," Tusk said Saturday.
He said the 27 leaders would unanimously have to say there was "sufficient progress" to allow the talks to go to the next phase. That would give any EU country with a dispute with Britain, like Spain over Gibraltar, major influence over the timetable of the talks.
The negotiating guidelines also halted British hopes of having future trade relations being discussed concurrently through the talks.
"Before discussing the future, we have to sort out our past. We will handle it with genuine care -- but firmly," Tusk said.
U.K. exit Secretary David Davis said Saturday that the sides were on the same page and that talks would be "tough and, at times, even confrontational." He warned that some people in the EU and U.K. are trying to undermine them.
May's administration has shown a willingness to give ground on key matters involving finance, trade and immigration. Still, some attendees of the summit already were considering how to deal with possible British negotiating tactics.
"Maybe the British government will do its utmost to split the 27 nations. It is a trap we need to avoid," Belgian Prime Minister Charles Michel said.
Ever since the June 23 referendum last year in which Britons narrowly voted to leave the bloc, the unity of the remaining 27 EU nations "has been really exemplary," German Chancellor Angela Merkel said.
In contrast, citizens in Britain have been divided over the looming changes.
The EU is also intent on making Britain pay a divorce bill, which some EU officials have put as high as $65 billion. The money aims to pay for everything from pensions to financial commitments already made in the EU's seven-year-budget, which runs until 2020.
Outgoing French President Francois Hollande said the leaders agreed on "a simple principle," applicable to Britain or any other country that might want to quit the bloc in the future, "that they must not be in a more favorable situation on the outside than they were on the inside."
"There is always a price, a cost, a consequence from quitting the Union," Hollande said at his farewell European summit.
To kick off the negotiations with Britain, Tusk wants to center on the millions of people who would be immediately affected.
All sides "need solid guarantees for all citizens and their families who will be affected by Brexit on both sides. This must be the No. 1 priority," Tusk said.
About 3 million citizens from the 27 nations live in Britain while up to 2 million Britons live on the continent, all facing uncertainty on such issues as health benefits, pensions, taxes, employment and education.
Tusk said the sustained unity of the 27 countries in the EU will help May since she will have political certainty throughout the talks.
"Our unity is also in the U.K.'s interest," he said.
Over the past years, the bloc has been divided over issues such as the financial crisis, the euro debt crisis, bailouts to financially strapped members like Greece and how to deal with the hundreds of thousands of migrants who have been entering the bloc.
The 27 EU leaders also acknowledged that Northern Ireland could join the bloc in the future if its people vote to unite with EU member Ireland. The two share the same island, and the difficulties of re-establishing a land border once the United Kingdom leaves the EU are politically fraught.
Irish Prime Minister E̶d̶n̶a̶ Enda* Kenny said that if a Northern Irish referendum to break away from the United Kingdom is approved "at some time in the future, EU membership is assured and is unanimously accepted by the European Council."
Kenny stressed that such a referendum was not in sight at this stage.
Future relations between Ireland and Britain, including how the border between Ireland and Northern Ireland would work with the U.K. outside the bloc, have emerged as a key problem.
Kenny conceded that EU unity will be tested once negotiations start, given the challenge of accommodating the sometimes-competing interests of the countries involved.
"It won't all be as calm and as measured as today," he said.
EU Commission President Jean-Claude Juncker already complained Saturday that "Britain currently blocks the decision-making" on a review of the EU's long-term budget.
"It would be good and it would make the start of the talks easier if Britain could lift its objection," Juncker said.
British officials have said the government prefers to postpone the decision on such an important matter as the EU budget until after the election is over.
"Obviously we will stand up for our interests as Britain, too, will stand up for its interests," Merkel said at a news conference after the summit meeting. "We're trying to forge a strong European Union of 27. This is the sort of spirit with which we approach these negotiations."
Saturday's adoption of the guidelines was followed by "a general round of applause," Merkel noted.
Information for this article was contributed by Raf Casert, Lorne Cook, Frank Jordans, Jan Olsen, Monika Scislowska and John Leicester of The Associated Press; by Ian Wishart, Stephanie Bodoni, Dalius Simenas, Tony Czuczka, Esteban Duarte, Lyubov Pronina, Nikos Chrysoloras, Stephanie Bodoni, Alexander Weber, Mark Barton, Viktoria Dendrinou, Marek Strzelecki, Ed Ludlow, Jones Hayden, Arne Delfs, Andrew J. Barden, John Follain, Marine Strauss, Radoslav Tomek and Jonathan Stearns of Bloomberg News; and by James Kanter of The New York Times.
A Section on 04/30/2017
*CORRECTION: Irish Prime Minister End Kenny said that if Northern Ireland holds its own referendum to break away from the United Kingdom, then its membership in the European Union would be accepted by EU leaders. A previous version of this story incorrectly spelled Kenny’s first name.