The government is expected to table a motion to hold a general election on 14 October if it is defeated by MPs opposed to a no-deal Brexit on Tuesday.
Boris Johnson said he did not want an election, but progress with the EU would be “impossible” if they won.
Tory rebels are joining forces with Labour to bring a bill designed to stop the UK leaving the EU on 31 October without an agreement.
It would force the PM to request a delay to 31 January 2020 in that event.
Speaking outside No 10, Mr Johnson insisted that with MPs’ backing, he would be able to achieve changes to the UK’s current Brexit deal – negotiated by Theresa May and rejected three times in the Commons – at an EU summit on 17 October.
But he said if MPs voted to block no deal they would “plainly chop the legs out from under the UK position”.
The PM said there were “no circumstances” in which he personally would ask Brussels to delay Brexit and UK negotiators must be allowed to get on with their work without interference from Westminster.
“I don’t want an election and you don’t want an election,” he added.
“Let us get on with the people’s agenda, fighting crime, improving the NHS, boosting schools, cutting the cost of living, and unlocking talent and opportunity across the entire United Kingdom.”
Faced with Mr Johnson’s promise to leave the EU on 31 October, with or without a deal, a number of MPs have come together across party lines to try to prevent the latter outcome.
They are expected to put forward legislation on Tuesday under Standing Order 24 – a Commons rule which allows urgent debates to be called.
The bill, which has now been published by Labour MP Hilary Benn, would force the PM to request a Brexit delay to 31 January 2020 unless MPs had approved a new deal, or voted in favour of a no deal departure, by 19 October.
Tory rebels – who include former ministers and prominent backbenchers – have been warned that those who support the legislation face being expelled from the party and deselected.
But leading figures, including ex-Justice Secretary David Gauke, have insisted that despite the threat, they will press ahead and – in their words – put the “national interest” ahead of their own.
Speaking at an event on Monday evening, Labour leader Jeremy Corbyn told supporters his party was ready for a vote, adding: “I will be delighted when the election comes.”
“I’m ready for it, you’re ready for it, we’re ready for it.”
He accused Mr Johnson of “threatening people with a no-deal Brexit if he doesn’t get his way in Parliament”.