Boris Johnson is considering seeking an early general election if MPs seeking to block a no-deal Brexit defeat the government this week.
The BBC understands “live discussions” are going on in No 10 about asking Parliament to approve a snap poll.
Political editor Laura Kuenssberg said it could happen as soon as Wednesday but no final decision had been taken.
Tory ex-ministers are joining forces with Labour to stop the UK leaving the EU on 31 October without a deal.
Amid mounting speculation about an election, Mr Johnson is due to hold an unscheduled cabinet meeting at 17.00 BST on Monday and will also speak to Conservative MPs.
The prime minister has said the UK must leave the EU on 31 October, with or without a deal, prompting a number of MPs to unite to try to prevent the UK leaving without an agreement.
They are expected to put forward legislation on Tuesday to stop no deal under “SO24” or Standing Order 24 – the rule allowing MPs to ask for a debate on a “specific and important matter that should have urgent consideration”.
Tory rebels have been warned those who support the move would be expelled from the party and deselected.
A No 10 spokesman said it was treating this week’s Brexit votes as an issue of confidence, which traditionally trigger a general election if the government loses.
But leading figures, including ex-cabinet minister David Gauke, have insisted that despite the threat of expulsion, they will press ahead with efforts to pass legislation requiring the PM to seek another Brexit extension if he cannot get a deal.
There is not scheduled to be another general election until 2022.
Under the terms of the Fixed Terms Parliament Act, Mr Johnson would require the backing of two-thirds of the UK’s 650 MPs to trigger an early poll this autumn.
Should this happen, the prime minister would be able to recommend the date of the poll – likely to be a hugely contentious issue – to the Queen.
If Parliament were dissolved on Friday then the earliest possible date for an election would be Friday 11 October. With polls normally taking place on a Thursday, 17 October is potentially the more likely earliest opportunity.
Labour leader Jeremy Corbyn has said the UK “needs” a general election, despite warnings from Tony Blair that such a vote would be “an elephant trap” for Labour.
The ex-PM warned on Monday that Mr Johnson could win such a vote as “some may fear a Corbyn premiership more” than a no-deal Brexit.
But Mr Corbyn said a vote “would give the people a choice between two very different directions for the country”.