The latest U.K. proposal on Brexit, as reported by media, is “fundamentally flawed” and “won’t fly,” European Union diplomats and officials say, adding that another delay to the U.K. departure is likely if it is London’s final offer for a deal.

“The proposal is fundamentally flawed,” a senior EU official said Wednesday, referring to details reported by media on what U.K. Prime Minister Boris Johnson said would be his final bid to get a deal done before the scheduled Oct. 31 departure.

“This won’t fly. Johnson has chosen a confrontation,” an EU diplomat dealing with Brexit said separately. “The remaining options are “the original, Northern Ireland-only backstop with some modifications, or an extension.”

Johnson will on Wednesday officially unveil his final Brexit offer to the EU and says that, if Brussels does not engage with it, the U.K. will stop talking and leave on Oct. 31 regardless.

In his closing speech to his Conservatives’ annual conference, Johnson will stick to his hard line on Brexit, offering the party faithful details of what he will describe as his “fair and reasonable compromise.”

The future of Brexit, the country’s most significant geopolitical move since the Second World War, is uncertain. It could leave with a deal or without one — or not leave at all.

“My friends, I am afraid that after 3½ years, people are beginning to feel that they are being taken for fools. They are beginning to suspect that there are forces in this country that simply don’t want Brexit delivered at all,” he (Johnson?) will say, according to extracts released by his office.

“Let’s get Brexit done on October 31 so in 2020 our country can move on.”

In a strategy that will define the future of Brexit, the EU and his premiership, Johnson is betting he can get enough concessions from Brussels to persuade Brexit supporters in the U.K. Parliament to ratify any deal.

Johnson has been firm the Oct. 31 deadline will be met, but Parliament has put roadblocks in his way, passing a law that requires him to ask the EU for a delay if he fails to secure an acceptable deal at an EU summit Oct. 17-18.

Early Tuesday, sterling had dipped to a one-month low of $1.2205 as traders became increasingly nervous about the possibility of a deal. On Wednesday morning, it was trading at $1.2228, weighed down by fears that Johnson’s proposal would not produce an agreement.

‘Moment of Truth’

The EU has repeatedly asked Britain to come up with “legal and operational” proposals for the changes Johnson wants to a deal that predecessor Theresa May negotiated with the bloc last year.

“This is the moment of truth,” Conservative Party chair James Cleverly said.

He said the EU must see the need to compromise if it wants to avoid a “no-deal” Brexit, which would mean no measures to soften the sudden rupture of trade and cooperation agreements that have been in force for decades.

A Brexit slogan is displayed on a window at the venue of the Conservative Party annual conference on Tuesday. (Phil Noble/Reuters)

Following its rejection three times by Parliament, Johnson has demanded changes to the withdrawal agreement, officially know as Article 50, especially over new arrangements with the bloc for the border between Northern Ireland, which is part of the U.K. and EU member Ireland.

But weeks of talks since Johnson took power have made little headway, and British officials described the proposal to be unveiled on Wednesday as a final offer.

The Telegraph cited a briefing to European capitals to report that the U.K. was proposing to leave Northern Ireland in a special trading relationship with the EU until 2025, after which Belfast would decide whether to remain aligned to the bloc or return to following U.K. rules.

The newspaper said London was proposing that Northern Ireland leave the EU customs union at the end of the transition period in 2021 alongside the U.K., which would move directly into a free trade agreement with Europe.

Customs checks would take place at a distance from the Ireland-Northern Ireland border, which will have become the border of the EU’s tariff-free internal market.

‘Nobody will work on delay’

The proposal would be aimed at replacing the so-called backstop — an insurance policy to prevent the return of a hard border on the island of Ireland — that has become the biggest hurdle to securing an agreement with Brussels.

A senior British government official said: “The government is either going to be negotiating a new deal or working on no-deal, nobody will work on delay.

“We will keep fighting to respect the biggest democratic vote in British history. The EU is obliged by EU law only to negotiate with member state governments, they cannot negotiate with parliament, and this government will not negotiate delay.”