Boris Johnson has insisted he does not want a general election, as he urged MPs not to vote for "another pointless delay" to Brexit.
Tory ex-ministers are joining forces with Labour to stop the UK leaving the European Union on 31 October without a deal.
Speaking outside No 10, Mr Johnson said such a move would make further talks with the EU on a new deal "impossible".
The BBC is reporting the PM would seek to call a vote, expected to be on 14 October, if MPs block no deal.
With MPs' backing, though, he said he would be able to achieve changes to the UK's current deal - negotiated by his predecessor Theresa May and rejected three times in the Commons - at an EU summit on 17 October.
The chances of reaching a new agreement had been "rising" because the UK was preparing to leave the EU "come what may" by the latest deadline, he added.
The British parliament returns on Tuesday from its summer break and an alliance of opposition lawmakers and some rebels in Johnson's party will seek to grab control of parliament to force him to delay rather than go for a no-deal Brexit.
Mr Johnson has already set in motion the the suspension of the UK parliament for five weeks ahead of 31 October, which would give MPs much less time to pass laws to stop a no-deal Brexit.
"I want everybody to know there are no circumstances in which I will ask Brussels to delay", Mr Johnson said at outside Downing Street today.
In an implicit warning to MPs he said: "We will not accept any attempt to go back on our promises."
"I don't want an election. You don't want an election. Let's get on with the people's agenda," he said.
Mr Johnson added that if MPs voted to delay Brexit they would "plainly chop the legs out from under the UK position and make any further negotiation absolutely impossible."
More than three years since the United Kingdom voted 52-48 percent to leave the European Union, it is still unclear on what terms, or indeed whether, Brexit will take place.
Mr Johnson's enforcers warned rebels that if they voted against the government they would be kicked out of his Conservative Party.
- BBC / Reuters