European capitals don't want to see Britain crashing out of the EU without a deal to smooth the Brexit transition, and would probably allow London to delay the divorce.
But if the remaining 27 EU leaders agree -- and they must be unanimous -- to push Brexit beyond March 29, it would only be after receiving solid guarantees from London.
Ideally, any delay would be used to ratify the withdrawal agreement signed by Prime Minister Theresa May in November but rejected this week by the British parliament.
Since the scale of the opposition became clear, there has been talk in Brussels of a delay lasting several months, not just for weeks as previously thought.
But diplomatic sources here swiftly dismiss such an idea as premature, insisting it is for May's government to come to EU negotiators with any plea for more time.
Could a way be found to delay Brexit even beyond the European elections in May or the start of the next parliamentary session in Strasbourg on July 2?
"There are many ideas going around. I'm sure that's one of them," a well-placed source told AFP, while stressing that London has yet to make any request.
'Better be quick'
EU Commission spokesman Margaritis Schinas said EU leaders would only address the question if May decides to ask it, and that Brexit Day remains March 29 for now.
Nevertheless, several diplomatic sources in the European capital confirmed that informal discussions of a delay had taken place while they wait for May's next move.
"It's not as easy as all that to give more time," one said, complaining of the mood of uncertainty.
"Businesses and citizens want to know if Britain is staying or going."
The timetable was set by Article 50 of the EU Treaty, which British lawmakers rushed to invoke in the wake of the 2016 Brexit referendum, setting a two-year deadline.
The European Court has ruled that Britain could simply revoke this notification if it decides to remain in the union after all, but it can not be unilaterally put on pause by London.
With the support of the 27, however, it could be suspended -- once -- to allow time to ratify of modify the accord, the diplomatic and European sources believe.
And it could, some say, be put on hold if Britain were to need to hold a general election or a second Brexit referendum, ideas which May has so far rejected.
Downing Street has not, however, managed to demonstrate that it can wield enough support for parliament to unite behind any vision of Brexit.
And Europe is loathe to kick the can down the road simply to allow more chaos in Westminster or give May more time to winkle concessions from EU negotiators.
"If they tell us they want to organise new elections or a referendum that would be one of the acceptable reasons," one diplomat told AFP.
"But it better be quick, not more than a few weeks."
Under EU law, member states must have MEPs in the European Parliament in Strasbourg. A new batch will be elected in May, with 27 of the 73 British seats assigned to other member states.
But if Brexit is delayed, Britain would have to hold one more European election, even if its members might only sit for a short period.
EU lawyers have warned that if a new parliament sits without the British, but with the UK still a member, anyone who wants to challenge laws passed by the new session could argue they are illegal.
Held for ransom
Another diplomat said EU capitals are concerned that Britain could use this loophole to hold the entire EU legislative process to ransom as leverage in exit talks.
"The realistic idea is a maximum delay until the opening session of the European parliament at the start of July," a source said.
Some expert observers, however, argue that Brussels could find a way to fudge this apparently hard deadline.
"It's a problem, of course, but one that can be overcome," argued Pierre Vimont, a former senior EU diplomat and a scholar at the Carnegie Europe think tank.
If Britain needs to hold EU elections, he told AFP, that could be seen as a kind of proxy referendum to test the pulse of British opinion.
In any case, the debate is academic as long as Number 10 doesn't ask for a delay.
"We have not discussed extending Article 50 with the EU," May's spokesman said Thursday.
"It has been raised in discussion with us but it's not something we've raised with the EU or suggested that we wish to do. Because we do not wish to do it."
