The prime minister called a surprise meeting of his top ministers to discuss the government’s response to MPs’ moves to block a no-deal Brexit on October 31.
Around 20 Tory rebels and opposition parties will on Tuesday begin moves to try and seize control of the Commons to pass their own legislation designed to block no deal.
The source said the cabinet will discuss “the government’s response to MPs seeking to take control of legislative agenda away from the government and handing it to the opposition and Jeremy Corbyn without the consent of the people”.
The view in Downing Street is that the move represents “an expression of confidence in the government’s negotiating position to secure a deal”.
The reference to a confidence vote has fuelled speculation that the PM could react to a defeat by calling a snap election.
But the source refused to discuss what might happen before knowing the result of any vote.
Johnson will chair cabinet at 5pm on Monday before addressing Tory MPs at a long-planned garden party at Downing Street at 6pm.
It comes as leading former cabinet minister David Gauke accused Johnson of “goading” Tory rebels so he can force a snap election having purged MPs opposed to no deal.
Johnson will need to win a two-thirds of MPs in the Commons to vote for a snap poll for it to take place, meaning he would almost certainly need Labour support.
Jeremy Corbyn is highly unlikely to back a snap election to take place after the October 31 Brexit date.
But he will be under huge pressure to go to the country as leader of the opposition if Johnson commits to an election before Brexit.
Earlier he told Sky News: “We are the opposition party, we want a general election”.
Ex-PM Tony Blair said Corbyn “might be tempted by an election” because he may “gain support from people who may not entertain his leadership” otherwise.
But he warned the Labour leader to ”see an election for the elephant trap it is”, warning that Johnson could win a majority which would leave him free to pursue no deal.
“If the government tries to force an election, Labour should vote against it,” Blair said.
Corbyn suggested he wants to first pass legislation to stop no deal before any election.
Speaking in Salford, he said: “First we must come together to stop no-deal - this week could be our last chance.
“We are working with other parties to do everything necessary to pull our country back from the brink. Then we need a general election.
“When a government finds itself without a majority, the solution is not to undermine democracy - the solution is to let the people decide, and call a general election.
“A general election is the democratic way forward, to give the people the choice between two very different directions for our country.”
Scottish First Minister Nicola Sturgeon said the SNP would back an election if it took place before the October 31 Brexit date.