Boris Johnson has said he is “not aiming for a no-deal outcome” for Brexit at the launch of his campaign for the Tory leadership.
But he said leaving no deal on the table was a “vital tool of negotiation” and the UK “must do better than the current withdrawal agreement”.
“Delay means defeat, delay means Corbyn,” he said, saying the UK must leave the EU on 31 October.
Home Secretary Sajid Javid will also make his pitch to MPs on Wednesday.
In a campaign video released on Tuesday, Mr Javid said he would bring a “fresh look” to the Conservative Party and was capable of healing the divisions caused by Brexit.
Mr Javid has won the backing of Scottish Conservative leader Ruth Davidson, who will introduce him at Wednesday’s event.
Meanwhile Labour has tabled a cross-party motion to stop a no-deal Brexit being pushed through by a future prime minister.
It plans to force a vote on Wednesday to give MPs control of the timetable on 25 June, so MPs would be able to introduce legislation to avoid a no-deal scenario.
Mr Johnson is regarded as the frontrunner in the contest, with many more endorsements from Tory MPs than any other candidate.
He has kept a low profile in the race to succeed Theresa May so far, his only significant intervention being a pledge – immediately criticised by his rivals – to cut income tax bills for people earning more than £50,000 a year.
Chief Secretary to the Treasury Liz Truss defended Boris Johnson from accusations he is refusing to appear in media interviews during his leadership bid.
“He has got nothing to hide,” she told Radio 4’s Today programme.
“The important thing is he is talking to parliamentary colleagues.”
At Wednesday’s launch, the former foreign secretary – who quit over Mrs May’s Brexit policy – said the UK “must” leave the EU on 31 October.
“We simply will not get a result if we give the slightest hint that we want to go on kicking the can down the road with yet more delay,” he said.
