But officials do not believe there will be any breakthrough until Brexit battles in the Commons have finished.
Jeremy Corbyn ordered his MPs to cancel any travel plans they have next month as he ramped up plotting to bring down the government.
The Labour leader wants to force a confidence vote in the government and was widely expected to call it as soon after MPs return to Parliament on September 3.
But potential Tory rebels are unlikely to back the explosive move if they believe there are other ways of stopping no-deal.
Boris Johnson prepares for Remainer ‘stunt’ to block no deal
Mr Johnson could meet German Chancellor Angela Merkel and French President Emmanuel Macron
Miss Abbott said: “One of the things we have to do is consult with other parties – it’s no good moving a vote of no confidence if the Lib Dems, for instance, are not going to vote for it.”
She added: “We are talking to all of the other parties in Parliament and, if we move for a vote of no confidence, we’ll want to do it with confidence that we can win it.”
Downing Street now believes September 9 is the crucial date for Remainers to pounce.
Shadow home secretary Diane Abbott admitted Labour has yet to secure any support
Boris Johnson wants to get Britain out of the EU by October 31
They are preparing for MPs to try to hijack Parliamentary business relating to Northern Ireland on that date to try to block no-deal.
“If MPs are going to pull some sort of political stunt then that would be the point when they would do it,” a government source said.
Constitutional experts have said Brexit opponents have little chance of stopping the country leaving without a withdrawal agreement.
But No 10 believes that if Brussels is considering any concessions to the divorce settlement they will only be offered after pro-EU MPs have exhausted all of their options in the Commons during the two weeks it sits in September.
Brexit: John Curtice outlines ways MPs could trigger election
A no confidence vote to force a general election is one of the options thought to be being plotted
Brussels is said to believe Mr Johnson is serious about leaving without a deal on October 31 if a new agreement cannot be reached.
“What has landed is that the EU now understands that we mean it when we say that,” the source said.
“It is significant that, for the first time, they do get that – but the EU is watching and waiting to see what happens in September and what MPs do to try to stop it.”