LONDON — Boris Johnson asked EU leaders to help him out on Brexit, and they told him: You're on your own, pal.

The prime minister fist-bumped the air and lauded the “blistering timetable” proposed by German Chancellor Angela Merkel to find an alternative to the Brexit backstop on Wednesday as the two held a joint press conference in Berlin. He was pleased as punch with what he clearly saw as a win, telling reporters: “I’m more than happy with that.”

“I see possibilities, shaping the future relationship, to address this point,” Merkel had said before the pair sat down to dinner. “It was said we will probably find a solution in two years,” she added. “We can maybe find it in the next 30 days.”

Much of the British press had a field day. “30 days to do a deal,” screeched the front page of the Daily Express. “30 days to ditch the backstop,” cried the Daily Telegraph. The Sun could hardly contain itself, with: “Can we do it? Ja, we can!”

But just hours after Merkel appeared to set the deadline, Downing Street became less excitable. “It’s not a literal deadline and wasn’t intended that way,” an official told POLITICO. “We are of course working at pace for a deal but only if the backstop is abolished.”

Those who felt Theresa May did not do enough to carve out the backstop may be happy, but the "alternative arrangements" plan is unlikely to fly with the EU.

The official was right that the deadline is not literal. “It is not about 30 days,” Merkel said at a news conference in The Hague on Thursday. “The 30 days were meant as an example to highlight the fact that we need to achieve it in a short time because Britain had said they want to leave the European Union on October 31.”

Merkel appears to have set Johnson a near-impossible task. The German chancellor made clear it is up to the U.K. to come up with a permanent solution that would remove the need for a backstop but offered no hint that the Withdrawal Agreement could be reopened. It would mean Johnson coming up with a long-term fix to the border problem that could be written into the Political Declaration on the future relationship.

Rather than opening a window of opportunity, she offered Johnson a rope on which to hang himself if the U.K. ends up leaving without a deal.

“What she was saying was: We are where we have always been,” said Anand Menon, director of the U.K. in a Changing Europe think tank, who sees the words from Merkel as part of a blame-game strategy.

“I’m sure they have thought this through in terms of what strategy is most effective for blame avoidance,” he explained. “And this is the way that the European Union can make it sound like they are being reasonable.”

The approach was cemented Thursday when French President Emmanuel Macron took the stage with Johnson in Paris. Macron said that without a workable proposal on the backstop, “it’s a British political problem and then it’s not negotiation that can solve it, it’s a political choice that the prime minister will have to make, not up to us.”

He added: “I’ll be very clear, in the next month we won’t find a new Withdrawal Agreement that will be very different from what we have."

Johnson will not be looking very far for a proposal. He cited a blueprint drawn up by the so-called Alternative Arrangements Commission, a group of mainly Conservative MPs that penned a document claiming an alternative system could be in place in three years. It suggested “special economic zones” around the Northern Irish border that would be exempt from normal regulatory requirements. It also proposed using trusted-trader schemes and said the Republic of Ireland should align with the U.K. on food safety regulations.

His support for the plan will rally some in the domestic audience. One Cabinet minister said: “The PM has managed to get alternative arrangements on the agenda now and the difference with this administration is that they will actually table them for discussion.”

Boris Johnson has a major challenge on his hands to meet his promise of Brexit by the end of October.

Those who felt Theresa May did not do enough to carve out the backstop may be happy. But the "alternative arrangements" plan is unlikely to fly with the EU, and would still need a longer transition period of up to three years.

Whether or not a deadline of 30 days exists, Johnson has precious little time to get anything agreed. EU leaders will be looking toward the European Council summit starting on October 17 as the key date to rubber-stamp something new. They will need some time before that to thrash out any new proposals and come up with a legal framework, which could explain why Macron wants “visibility” in the next month.

And then there is the U.K. parliament. Any deal will have to be voted on in the Commons and then be laid out in a bill to implement the details into U.K. law. That bill would include transition issues and the divorce settlement — touch-paper issues for some MPs. Then it will have to pass through the Lords, which the government has no control over.

“In terms of the legislative challenge, it would be remarkable if a bill of the complexity of the 'withdrawal agreement bill' were to be pushed through in (even) a month to six weeks, let alone a fortnight,” one legislative expert said via text message. As a best-case scenario, they predicted a technical extension to cover the legislation or a desperate rush to meet the October 31 deadline, probably with a reduced or cancelled conference recess.

Johnson has a major challenge on his hands to meet his promise of Brexit by the end of October. And EU leaders have made sure the challenge is all his.

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