EU ambassadors will meet in Brussels tomorrow with the aim of agreeing the terms of an extension to the 31 October Brexit deadline.
They have already agreed to the principle of a three-month extension, but must now decide on whether it should be a flexible deadline.
Diplomatic sources say ambassadors are considering whether to allow the UK to leave the EU on either 1 December or 1 January if the Withdrawal Agreement is passed by the House of Commons the previous month.
British Prime Minister Boris Johnson reluctantly requested a three-month delay from the EU last week, after his Brexit bill was blocked in Parliament.
It has resulted in Mr Johnson proposing that a general election to take place on 12 December if MPs allowed the Brexit bill to pass all stages by Wednesday next week.
However, due to the UK's Fixed Term Parliament Act, Mr Johnson cannot unilaterally call an election and requires opposition support which has not been forthcoming.
This weekend the Scottish Nationalist Party and Liberal Democrat's called for an election on 9 December, if the possibility of a crash-out Brexit was off the table.
However, the Labour leader Jeremy Corbyn dismissed the suggestion as nothing more than a "stunt".
EU ambassadors considering the extension to the Brexit deadline must vote unanimously for any proposal and France has been pressing for the shortest possible extension.
Whatever is agreed by the EU ambassadors needs to be signed off by EU capitals.
One consequence of an extension being granted is that the EU would ask the UK to nominate a candidate for the new European Commission.
A draft text to be considered by EU Ambassadors, and seen by the Guardian newspaper states: "In the event that the parties to that agreement complete their respective ratification procedures and notify the depositary of the completion of these procedures in November 2019, in December 2019 or in January 2020, the withdrawal agreement will enter into force respectively on [the first of the month of the relevant month]."
