The European Union will delay Brexit until February 2020 if Boris Johnson is unable to get his deal past MPs this week, according to reports.
Diplomatic sources quoted by The Times said a delay would be "fungible" - meaning Britain could leave on select earlier dates if the PM's deal is ratified by then.
A decision on granting an extension to the October 31 deadline will not be made until EU governments have assessed the chances of the deal getting through Parliament before Tuesday this week, according to the publication.
Its sources said the EU’s most likely option is to decide that the three-month extension in the Benn act - until January 31 2020 - is a purely “technical extension”.
Meanwhile, EU diplomats and officials said on Sunday that, depending on the next developments in London, extension options range from just an additional month until the end of November to half a year or longer.
It comes after the Prime Minister was required by law to ask the EU for an extension after MPs voted in favour of Sir Oliver Letwin's amendment in the Commons yesterday.
But in a move which sparked a major backlash, Boris Johnson got a senior diplomat to send an unsigned photocopy of a letter asking for an extension.
Meanwhile, Michael Gove insisted earlier on Sunday that Britain would leave the EU by Halloween.
Mr Gove told Sky News's Sophy Ridge On Sunday: "We are going to leave by October 31st. We have the means and the ability to do so and people who - yesterday we had some people who voted for delay, voted explicitly to try to frustrate this process and to drag it out.
"I think actually the mood in the country is clear and the Prime Minister's determination is absolute and I am with him in this, we must leave by October 31st."
The Chancellor to the Duchy of Lancaster said the Government will trigger Operation Yellowhamer, their contingency plan to handle a no-deal Brexit.