Boris Johnson has said he will give MPs more time to debate his Brexit deal, but only if they agree to a 12 December general election.
The prime minister told the BBC he expected the EU to grant an extension to his 31 October deadline, even though he “really” did not want one.
He urged Labour to back an election in a vote he plans to hold next week.
The EU is expected to give its verdict on delaying Brexit for three months, or less time than that, on Friday.
In a letter to Labour leader Jeremy Corbyn, Mr Johnson says his “preferred option” is a short postponement “say to 15 or 30 November”.
In that case, he writes, he will try to get his deal through Parliament again, with Labour’s support.
The prime minister adds that he “assumes” Mr Corbyn “will cooperate with me to get our new Brexit deal ratified, so we leave with a new deal rather than no deal.”
If, as widely expected, the EU’s Brexit delay is to the end of January, Mr Johnson says he will hold a Commons vote next week on a 12 December election.
If Labour agrees to this, the government says it will try to get its deal through before Parliament is dissolved for the campaign on 6 November.
“If they (MPs) genuinely want more time to study this excellent deal, they can have it – but they have to agree to a general election on 12 December,” Mr Johnson told BBC political editor Laura Kuenssberg.
Asked what he would do if Labour refused to vote for an election, he said: “We would campaign day after day for the people of this country to be released from subjection to a Parliament that has outlived its usefulness.”
Speaking earlier, before the PM’s latest offer, shadow chancellor John McDonnell said Labour was ready for a general election “whenever it comes”, but he refused to be drawn on whether his party would back one if Mr Johnson held a vote on it next week.
“We will see what happens. We are trying to take this in stages,” he said.
Mr McDonnell said Labour remained open to a “compromise” with the government, which could allow Mr Johnson to get his Brexit deal through Parliament.