(CNN) When Emmanuel Macron and Boris Johnson spoke to reporters ahead of their meeting in Paris on Thursday, they stood side by side but sounded as if they were living in parallel universes.
Both men stuck firmly to their lines -- the British Prime Minister demanding that the European Union reopens the Brexit agreement, the French President saying that's not possible.
Macron said that he's often portrayed as the "hard man" in Brexit negotiations. But there is little time left to alter the existing deal substantively, he said. "We will not find a new withdrawal agreement within 30 days which will be very different from the existing one."
The French President reiterated his stance that Brexit is "not the choice of the European Union."
Johnson's Paris visit was the second leg of a trip aimed at pushing the European Union to shift its position on Brexit. The PM insists the EU must ditch the so-called Irish backstop -- a demand that has so far fallen on deaf ears among the bloc's leaders.
"The Irish backstop (clauses) are not simply technical constraints but vital guarantees for the preservation of stability in Ireland and the integrity of the single market which is the basis of the European Project," Macron added.
"Where there's a will, there's a way," Johnson said.
But when asked what the plan was, the prime minister fell short of delivering a concrete answer.
Instead, he referred to "an excellent paper" published by a group of British lawmakers which outlined alternative solutions earlier this year. However, that proposal has already been rejected as unworkable by the European Union.
It was always going to be a tough meeting for Johnson. The French President made it clear earlier that he won't be persuaded to change his position in talks with Johnson. According to Reuters, Macron on Wednesday warned renegotiation was "not an option that exists," adding that Britain could become the "junior partner of the United States" after a no-deal Brexit.
"Can the cost for Britain of a hard Brexit -- because Britain will be the main victim -- be offset by the United States of America? No. And even if it were a strategic choice it would be at the cost of a historic vassalization of Britain," Macron said.
In his opening remarks, Johnson tried to highlight the good relationship between the two countries, mentioning the French and British troops working side by side in Mali and Estonia. He then pointed out that buses made in France are traversing London's streets and that French high-speed TGV trains run on British steel rails.
But the charm offensive didn't seem to have much effect, as Macron kept insisting the backstop clause was indispensable.
The backstop clause is designed to prevent the return of a hard border between Northern Ireland, which is part of the UK, and the Republic of Ireland, an EU member. It was negotiated by Johnson's predecessor Theresa May, but widely criticized by UK lawmakers who still need to ratify the agreement to stop the country from crashing out of the bloc without a deal.
However, the European leaders are sticking to their line: if Johnson wants to remove the backstop, he needs to come up with a specific alternative proposal.
Speaking at a joint news conference in Berlin on Wednesday evening, German Chancellor Angela Merkel said the "UK has to tell us what ideas it has" to solve the backstop issue, adding that "it is not the job of the chancellor" to find a solution.
Merkel challenged Johnson to come up with a new plan for Brexit in 30 days.
European Council President Donald Tusk said on Tuesday the backstop was "an insurance to avoid a hard border on the island of Ireland unless and until an alternative is found."
"Those against the backstop and not proposing realistic alternatives in fact support reestablishing a border. Even if they do not admit it," Tusk added.
A lack of a Plan B would mean the UK is more likely to crash out of the EU without a deal. This would, according to the government's own forecasts, plunge the country into economic chaos. It could also spark food, medicine and fuel shortages.
Johnson has indicated he is prepared to take the country out of the EU without an agreement.