The EU says it is ready to extend the post-Brexit transition period if the UK wants.
The current length of the transition period – designed to smooth the path from Brexit to the UK and EU’s future permanent relationship – is 21 months.
But with the two sides failing to reach a deal yet, UK Prime Minister Theresa May has suggested extending this arrangement “for a few months”.
Some Brexit campaigners have reacted angrily to the suggestion.
And an EU source told the BBC there would have to be “financial implications” if the UK did extend the transition period.
EU Council president Donald Tusk spoke to journalists at the end of a Brussels summit where there was no major breakthrough on how to avoid new visible border checks between Northern Ireland and the Republic after Brexit.
He said that if “the UK decided an extension of the transition period would be helpful to reach a deal, I am sure the leaders would be ready to consider this positively”.
Mr Tusk declared himself in a “much better mood” than after the last summit, in Salzburg.
Jean-Claude Juncker, the president of the European Commission, said extension of the transition period “will probably happen” saying it was a good idea because it would allow room to draw up a long-term relationship between the UK and the EU.
Earlier Mrs May said earlier that the extension of the transition period was a new idea that had emerged in negotiations and was not expected to be used.
The UK leaves the EU in March, and the current plan is for a 21 month transition period, which is designed to cover the gap between Brexit and the permanent future UK-EU relationship being in place.
Mrs May addressed her 27 European counterparts on Wednesday evening, urging them to give ground and end the current Brexit deadlock.
Speaking on Thursday morning, Mrs May said that the UK had already put forward a proposal to avoid the need for a return to Northern Ireland border posts or a customs border between Northern Ireland and the rest of the UK.
She added: “A further idea that has emerged – and it is an idea at this stage – is to create an option to extend the implementation period for a matter of months – and it would only be for a matter of months.
“But the point is that this is not expected to be used, because we are working to ensure that we have that future relationship in place by the end of December 2020.”
What the issue is
The UK is due to leave the EU on 29 March 2019, and the transition period, which Mrs May prefers to call the implementation period, is designed to smooth the path to a future permanent relationship.
During this transition period, which is due to finish on 31 December 2020, the UK’s relationship with the EU will stay largely the same.
The UK has signed up to the principle of agreeing an Irish border “backstop” – an insurance policy designed to prevent the need for customs checks – in case there is a gap between the transition period and the future permanent relationship coming into force.
The problem is that the two sides have yet to agree what form the backstop will take, and how long it could last.
Reaction to the idea of a longer transition
Asked whether he would support a longer transition period, Labour leader Jeremy Corbyn said: “The prime minister has got herself into this mess by failing to reach any meaningful agreements with the EU”.
Brexiteers were not impressed, with Conservative backbench MP Jacob Rees-Mogg telling Sky News it was “a rather poor attempt at kicking the can down the road”.
The Leave Means Leave campaign said a longer transition would give the EU “zero incentive to negotiate anything and gives Brussels the power to force whatever they want on to the UK”.
Speaking on BBC Radio 4’s Today programme, former Conservative minister Nick Boles described extending this period as as “desperate last move” and warned that Mrs May was losing the support of the Tory party.
Another former minister, Remain-voting Nicky Morgan, said an extension would be “unhelpful” and would leave the UK in a “Brexit holding pattern”.
Cabinet Office Minister David Lidington said the cost of extending the transition period would have to be “teased out” during the negotiations.
Irish Prime Minister Leo Varadkar said a longer transition period was not a substitute for a concrete agreement over the backstop.
But he said the idea would have some merit, adding “if it did help to reassure people that the backstop would never be activated, that would be a positive thing”.