The European Union believes Britain will not be ready to make a full break from the bloc by the end of 2020 as Brexit transition plans foresee and several senior EU figures said they are bracing for a much longer goodbye.
The British government may be thinking on similar lines.
Several diplomats and Brussels officials said a host of unresolved issues, including the Irish border, and British in-fighting over what kind of future trade relationship to ask for left many convinced the transition will end up being longer.
EU officials said British negotiators appeared to be sounding out other governments' attitudes to an extension to the 21-month transition currently on offer, although others said they believed British Prime Minister Theresa May still aims to have a free trade deal negotiated to start in January 2021.
As formal talks on the transition got under way in Brussels this week, EU diplomats said any extension would be agreed only after Britain formally leaves in March 2019, so that London would remain under pressure to conclude a trade deal or face its economy going off a "cliff edge" from 2021.
The bloc also says all the outstanding issues - including Ireland - must be solved for any transition to start after Brexit, due in March, 2019.
"If we don't have a ratified withdrawal agreement by the Brexit date, there will be no transition period. Britain will just crash out. Au revoir," said a senior EU diplomat.
Sources in Brussels acknowledge May cannot ask to prolong a transition which, by binding London to EU rules and budgets without having a say on them, is deeply unpopular with Brexit supporters:
Michel Barnier, the EU chief negotiator, after talking with May and Brexit Secretary David Davis in London on Monday, told EU envoys that a number of issues were proving difficult in talks.
British negotiators are due to update Barnier on their vision for London's future ties with the EU in Brussels on Friday, but there is little hope they would offer the clarity the bloc is demanding.
