UK Prime Minister Boris Johnson warned MPs that voting against the government would "chop the legs out from under" the UK's negotiating position after convening an unscheduled emergency cabinet meeting Monday evening.
"There are no circumstances in which I will ask Brussels to delay," Johnson said from a lectern outside 10 Downing Street.
"I don't want an election. You won't want an election," he added.
One expert said Johnson's insistence that he didn't want an election was a "framing device" and that if MPs vote for a delay tomorrow, Johnson could call a snap election
Many experts and journalists agreed.
British bookmakers unanimously slashed odds on a General Election taking place in 2019, with some firms going as short as 1/6 that it takes place this year, which would be about the equivalent of an 86.7% chance of an election, according to bookmakers' aggregator Oddschecker.
Protesters chanted "stop the coup" and booed as Johnson spoke.
Johnson's announcement came after UK Labour MP Hilary Benn unveiled details of a "cross-party" bill to stop a no-deal Brexit.
Scotland's first minister Nicola Sturgeon tweeted that it was "obvious" that Johnson "has no plan to get a deal."
Asked if Johnson was planning an election, his spokesman said earlier on Monday: "He has been asked this on many, many occasions and his answer has always been that he doesn't want there to be an election."
Sterling dropped more than 0.8% to as low as $1.2067 - a two-week low - as talk of an imminent election mounted.
Johnson's ultimatum to rebels
Conservative MPs have been warned they risk being kicked out of the party if they defy Johnson’s plan to leave the European Union with or without a deal on October 31.
A senior source from the whips office, which enforces party discipline in parliament, has told lawmakers they will not be allowed to stand for the Conservatives in the next election or be able to sit with the party in parliament now if they vote against the government on Brexit.
It comes ahead of an explosive week in Britain’s parliament, as opposition MPs backed by a significant number of Tory rebels plan to push through legislation that would force Johnson to extend Article 50 unless a deal could be reached with the EU before the Brexit deadline.
Conservatives including party veteran Ken Clarke, former Chancellor Phillip Hammond and leadership campaigner Rory Stewart have pledged to back efforts to prevent no-deal.
Labour leader Jeremy Corbyn has branded Johnson’s decision to suspend parliament from September 12 ahead of a Queen’s speech on October 14 an “attack on democracy”. Thousands took to the streets over the weekend to protest the decision.
Any deselection of MPs would deprive Johnson of his parliamentary majority - currently just one MP - and increase the chances of an early election in Britain.
British education minister Gavin Williamson said on Monday it would be right to deselect any lawmaker from the ruling Conservative Party who votes against the government on Brexit.