British Prime Minister Boris Johnson heads to Paris on Thursday for talks with French President Emmanuel Macron who is expected to rebuff his last-ditch efforts to renegotiate the UK's withdrawal from the European Union.
Macron, who has said previously he is happy to be the "bad guy" on Brexit, roundly rejected Johnson's calls to scrap a key plank of a deal negotiated between the EU and former British premier Theresa May.
"Renegotiation on the terms currently proposed by the British is not an option that exists, and that has always been made clear by (EU) President Tusk," Macron told reporters on Wednesday evening.
At stake is the so-called "backstop", an arrangement guaranteeing that border checks will not return between EU member Ireland and Northern Ireland which is part of Britain.
Johnson considers the backstop to be "anti-democratic" and an affront to British sovereignty because it will require London to keep its regulations aligned with the EU during a transition exit period.
The EU argues this is necessary to avoid the re-emergence of border checkpoints which could lead to a return of fighting on the divided island where anti-British violence has claimed thousands of lives.
The Paris visit is the second leg of Johnson's first foreign trip since he became prime minister a month ago.
On Wednesday, he told German Chancellor Angela Merkel in Berlin that the backstop has "grave defects for a sovereign, democratic country like the UK" and insisted the provision "has to go".
Merkel appeared to offer a glimmer of hope by saying Britain should try to find a breakthrough to the issue over the next month.
In the search for a solution, "we have said we would probably find it in the next two years, but maybe we can do it in the next 30 days, why not? Then we are one step further in the right direction," she said.
Johnson told Merkel he welcomed the "very blistering timetable of 30 days," adding that "I'm more than happy with that".
The remarks fit a pattern in which Merkel has often been more conciliatory in public about Brexit than Macron, whose abrasive remarks have sometimes caused anger in London.
"There is not the width of cigarette paper between Paris and Berlin on these issues," a Macron aide said on Wednesday on condition of anonymity.
Macron risked further irritating Johnson, whom he described in 2017 as having "no strategic vision", with a series of bruising remarks during his lengthy press conference on Wednesday evening.
He said the 2016 Brexit referendum had posed a question to the British people about EU membership "perhaps in a simplistic fashion" and without telling voters how the withdrawal would be achieved.
"Many lied about how it would be done," he added in another attack on Brexit campaigners, of which Johnson was the most high profile.
Johnson, who has deployed his French language skills to charm diplomats in Paris before, has staked his leadership on withdrawing Britain from the EU by the current deadline of October 31 -- "do or die".
His tough stance is seen by the French as making a "no deal" Brexit the most likely scenario and Paris has briefed journalists that it would be prepared to see Britain crash out of the EU rather than yield to Johnson's demands.
Some analysts see a risk of relations between Macron and Johnson becoming stormy in public, which could lead to a blame game about a "no deal" Brexit that is expected to wreak major economic damage on Britain and the EU.
Johnson reportedly once called the French "turds" over their stance on Brexit during his time as foreign secretary -- remarks he later said he could not recall.
But Macron pre-empted any attempt to deflect blame onto the European side.
"It will be the responsibility of the British government, always, because firstly it was the British people that decided Brexit, and the British government has the possibility up to the last second to revoke Article 50," he said.
Article 50 is the legal mechanism used by EU members states to withdraw from the bloc which was triggered by Britain in March 2017.
At the weekend, Macron, Merkel and Johnson will meet US President Donald Trump, a vocal supporter of both Brexit and Johnson, and the leaders of Canada, Italy and Japan at a G7 summit in the French seaside resort of Biarritz.