By Alastair Macdonald and Robin Emmott
BRUSSELS (Reuters) - European Union leaders warned Britain on Friday it had a final opportunity to leave the bloc in an orderly fashion after giving Prime Minister Theresa May two weeks' reprieve until April 12 before Britain could tumble out without a deal.
Arriving for a second day of a summit dominated by talks over Britain's departure, Belgium's prime minister said he hoped for a "rational" decision by British lawmakers to back the withdrawal treaty that May concluded with Brussels.
Preparations for a no-deal, in which Britain would face sudden trade barriers and restrictions on business, still were underway, however, Charles Michel told reporters.
"This is perhaps the last chance for Britain to say what it wants for the future," Michel said. "More than ever, this is in the hands of the British parliament," he said, adding that the 27 EU leaders were not blind to the risks of a no-deal.
Seven hours of summit brainstorming on Thursday kept a host of options open for leaders, who say they regret Britain's decision to leave but are eager to move on from what they increasingly see as a distraction.
A first-ever leaders dinner debate over the EU's China policy at the summit was delayed until Friday, for example.
May, who met leaders at the summit but missed out on the dinner because the 27 were forced to focus on Brexit rather than China, originally wanted to be able to delay Britain's departure until June 30 to tie up legislative loose ends.
But now, a May 22 departure date will apply if parliament rallies behind the British prime minister next week. If it does not, Britain will have until April 12 to offer a new plan or choose to quit the bloc without a treaty.
That date corresponds to the six weeks' legal notice required for the EU election - which the bloc would insist Britain hold on May 23 if it remains a member. If it does not hold the election, leaders said, the very last date Britain must leave would be June 30, before the new EU parliament convenes.
"We wanted to support May and we showed that," German Chancellor Angela Merkel told reporters. "It was an intensive, but successful evening."
A senior EU official said the key achievement was to shift the focus of responsibility to London from Brussels.
May will not attend the second day of the summit but will return to London to seek support for the withdrawal agreement.
DEPARTURE DETAILS STILL VAGUE
French President Emmanuel Macron argued at the summit that if the leaders left their decision until late next week, they would be seen as either pushing Britain out on Friday or blinking at their own deadline.
Instead, they have pushed the trigger back to Britain, which will be confronted by a choice by April 12 on whether to hold an EU election as part of a long-term rethink or prepare to quit by May 22, or possibly in June, without a deal.
"Everything is now in the hands of the House of Commons. That's the message," a senior EU official said.
The details of exactly how and when Britain would leave on or after April 12 are still somewhat vague.
It might leave abruptly at midnight (2200 GMT) on that Friday night. But EU officials said it could also agree a date with the EU to leave later, deal or no deal.
That could give some weeks to make a no-deal exit somewhat less chaotic, though the EU will refuse attempts to try and emulate the smoothness of the withdrawal treaty.
It would also try to insist on Britain being out by May 22 to avoid any problems over the EU election on May 23-26, but some leaders indicated that they could cope with Britain leaving any time until June 30 - before the new European Parliament convenes on July 2.
(Additional reporting by Robin Emmott, Philip Blenkinsop, Richard Lough, Francesco Guarascio, Andreas Rinke; Editing by Jon Boyle)