EU leaders are to consider a Brexit extension of between three and six months unless a final roll of the dice by Boris Johnson brings a miraculous breakthrough.
The British prime minister will set out his preferred alternative to the backstop within the next 24 hours, promising "this is the moment the rubber hits the road".
But there is little optimism in Brussels that it will resolve a three-year-old debate over how to maintain an open Border in Ireland.
Mr Johnson's plan is to include the creation of an all-island 'economic zone' for agriculture and food products.
However, the UK is likely to still rely on technology and loosely defined "alternative arrangements" to deal with the collection of cross-Border customs duties.
Sources told Independent.ie this would not meet the EU's requirements and therefore the chances of a deal ahead of October 31 would die.
As a result, EU leaders will have to begin negotiations on the possibility of another Brexit extension.
Under UK law, Mr Johnson is required to ask for a delay of at least three months if he can't secure a deal.
However, some countries are understood to believe this would not be a sufficient window for the UK to hold a general election and a new government to form a coherent plan.
Several EU leaders, including Taoiseach Leo Varadkar, have previously expressed concern about the creation of rolling Brexit deadlines.
This means a six-month period, which would see a new Brexit date of April 2020, is on the table.
While a debate over the length of an extension is likely, sources say there will be little resistance to a fresh delay.
EU chiefs believe they could not refuse a postponement if it was requested on the grounds that the UK wants to have a general election.
Irish MEP and first vice-president of the European Parliament Mairead McGuinness said while many in Brussels will have reservations "an election is as good a reason you would get to grant an extension".
"If you don't grant one, what do you end up with? A mess anyway," she said.
She added that members of the House of Lords have urged her to be aware that a January deadline "will not be sufficient".
"Because there will be an election in the UK in November. And then by the time it settles down, you're into the new year so we won't have time to get a deal by January. So the story that keeps giving keeps giving," she said.
The French parliament heard a much more fatalistic assessment yesterday when the country's foreign minister predicted a disorderly Brexit at the end of this month.
"Today, the hypothesis of an exit without agreement is the most plausible one, but the British have to say how they see the future," said Jean-Yves Le Drian.
Mr Johnson has sought to rubbish reports the UK was proposing customs checks on both sides of the Irish Border with a buffer zone in between.
He has always maintained that he would not allow the installation of border infrastructure but the idea was contained in so-called 'non papers' submitted by his government to the EU's chief Brexit negotiator Michel Barnier in recent days.
The EU immediately rejected the proposal, saying it failed to match the objectives of the backstop.
"Those checks don't need to take place at the Border...they don't need to involve new infrastructure," said Mr Johnson.
However, he added: "You must have checks of some kind. They can be checks between importer and exporter, the expediter and the recipient, there are ways of managing it that don't involve physical infrastructure and aren't laborious."
In the Dáil, Mr Varadkar said he had not seen the 'non papers', but welcomed the prime minister's words when he "disowned" the proposals.
He said the UK government promised no hard Border or associated controls or checks, adding that he expected the British government to honour its promises made in the Withdrawal Agreement.
"People here don't want a customs border between north and south and no British government should seek to impose customs posts against the will of the people on the island of Ireland," he said, adding, "I'm interested in what Northern Ireland businesses have to say."