Brussels: European Union leaders unanimously adopted a "firm and fair" Brexit strategy at a special summit on Saturday in a show of unity ahead of two years of tough talks with Britain.
The 27 leaders agreed the negotiating guidelines within minutes and applauded as they met in Brussels without Britain -- for the first time since Prime Minister Theresa May triggered the divorce a month ago.
They say talks on a future trade deal with Britain can only start once London agrees divorce terms on citizens' rights, its exit bill and the border in Northern Ireland.
EU President Donald Tusk hailed the "outstanding unity" among the leaders, saying it was a "firm and fair political mandate" for the Brexit negotiations.
"After four minutes we were ready, it's very promising," Tusk told a news conference, adding it was the "first time in our history" the notoriously divided club had moved so quickly.
European Commission head Jean-Claude Juncker said May had repeatedly urged him to be "patient" when they had dinner in London this week, but said Britain now needed to get serious about the talks.
"I have the impression sometimes that our British friends, not all of them, do underestimate the technical difficulties we have to face."
Brexit has offered the EU a fresh chance at unity after years of bitter internal divisions over the euro and migration.
May's decision to call a general election in Britain on June 8, in a bid to shore up her mandate and strengthen her negotiating position, has stiffened their resolve.
The British premier this week accused the EU of ganging up on London, in a war of words with German Chancellor Angela Merkel, who said Britain had "illusions" about the talks.
But Merkel insisted that "no one is allied" against London and that the EU was merely protecting its interests in the wake of Britain's historic vote to leave last June.
Merkel said the 27 leaders had given a round of applause after "very quickly" adopting the guidelines.
French President Francois Hollande meanwhile praised their common position and said there would "inevitably be a price and a cost for Britain."
The EU's chief Brexit negotiator, Michel Barnier, insisted the unity was "not directed against Britain" and that it was in London's interests for a quicker deal.
The EU 27 have considerably toughened the guidelines since Tusk first unveiled them a month ago.
Tusk said citizens' rights -- the fate of three million EU nationals living in Britain and one million Britons on the continent -- was the "number-one priority."
The former Polish premier urged a "serious British response", adding: "I want to assure you that as soon as Britain gives real guarantees for our citizens, we will find a solution rapidly."
The guidelines say that trade talks can begin only when EU leaders unanimously decide "sufficient progress" has been made on divorce issues.
Merkel said Barnier told the leaders he hoped for agreement on the divorce phase by autumn, so the talks can move onto a trade deal.
However, Britain says it wants to discuss the divorce and a trade deal in parallel.
In a further move that will rile London, the EU 27 also backed automatic membership for Northern Ireland if it reunifies with Ireland, and called for Spain to have a say over any deal that affects Gibraltar.
They discussed for the first time the spoils of Brexit -- the relocation of EU medical and banking agencies currently based in London.
While the EU says citizens' rights is a priority, the most touchy issue of all is likely to be Britain's exit bill.
This is estimated at around 60 billion euros ($65 million), which mainly covers financial commitments made by the bloc while Britain was a member.
The bill is politically toxic for Britain, though it also risks causing divisions among EU states as they debate how to plug any holes in the EU's budget.
Actual Brexit negotiations are not expected to begin until after the British election, although the EU is set to give an official mandate to Barnier on May 22.