Boris Johnson will write to the EU seeking another Brexit extension if a deal has not been agreed by October 19, according to government papers submitted to a Scottish court.
It contradicts the UK's prime minister previous claims he would "rather be dead in a ditch" than ask for a Brexit extension beyond October 31.
British MPs passed legislation — which Johnson refers to as the "Surrender Act" — last month that obliges the PM to ask Brussels to kick the Brexit deadline down the road if a deal is not agreed around the time of an EU summit in mid-October.
Johnson insists, however, the UK will leave the EU, with or without a deal, at the end of this month.
But this claim has been brought into doubt by a legal challenge in Scotland that seeks to impose "fines and imprisonment" if Johnson does not comply with the legislation.
In submissions to the Scottish court, the government said that Johnson accepted that he was obliged to send a letter to the EU asking for a delay and that, if an extension was granted, Britain would also agree to it.
"In the event that neither of the conditions set out ... is satisfied he will send a letter in the form set out in the schedule by no later than 19 October 2019," said the document posted on Twitter by Jo Maugham, an anti-Brexit lawyer involved in the case.
Separately, Irish Prime Minister Leo Varadkar said on Friday that he would consider an extension to the if the UK requested one, adding that an extension would be preferable to the UK crashing out of the EU.
"My preference is that we come to an agreement and that we have a deal by the middle of October," Varadkar said during a meeting with Danish Prime Minister Mette Frederiksen in Copenhagen.
"But if the UK government were to request an extension, of course, we would consider it. But I think most EU countries would really only consider it for a good reason, and that reason would have to be put forward. But certainly, an extension would be better than 'no deal'," he said.
Johnson has also previously said that Britain will leave the EU, "do or die", on October 31. His various contradictory statements remain unexplained, prompting speculation that he will seek a legal escape route or pressure the EU into refusing an automatic extension request.
Friday's court case comes just over a week after Johnson was humiliated by a landmark Supreme Court ruling that he had suspended parliament unlawfully.