UK members of Parliament are due to vote this Monday on the government's call to have an election on 12 December. Boris Johnson said if the motion was approved, his Brexit bill would resume its progress through Parliament until that is dissolved on 6 November.
Two-thirds of MPs - 434 - would have to back the motion for it to pass under the law which sets election timings.
Meanwhile EU ambassadors from the other 27 nations will meet to consider the date of a Brexit deadline extension. They have agreed tp delay Brexit and are expected to make a decision on a new date, with an option for the UK to leave earlier if and when a deal is signed off.
A draft text of an agreement for the ambassadors includes multiple possible dates for Brexit: 30 November, 31 December or 31 January.
There will also be a commitment that the Withdrawal Agreement on the UK's exit from the EU cannot be renegotiated in future.
In Westminster, the prime minister may not get the backing he requires for an election on the date he has chosen.
Jeremy Corbyn has said Labour is not prepared to support it until the risk of a no-deal Brexit is ruled out.
The SNP has said it will block the government's election attempt.
Along with the Liberal Democrats, the party is pushing for an election on 9 December - provided the EU grants a Brexit extension until 31 January.
They have proposed a bill which would tweak the Fixed-term Parliaments Act 2011 - the law which sets the time-frame for elections. That would need a simple majority of MPs.
A Number 10 source said on Sunday that MPs would vote on an election so we can get a new Parliament.
If the vote was lost, they said the government would then look at all options including ideas similar to those proposed by other parties.
MPs have already twice rejected a call from the PM to hold a general election.