Tensions between France and Germany driven by differences over nuclear energy and combustion engines cast a shadow over a meeting of the 27 European Union leaders Thursday.
Existing strains deepened between the European Union's two biggest players after Berlin upset some of its partners by blocking, at the last minute, a landmark deal to prohibit new sales of fossil fuel cars from 2035.
The ban is key to Brussels' ambitious plan to become a "climate neutral" economy by 2050, with net-zero greenhouse gas emissions.
In an unprecedented move this month, Germany intervened after the car ban had already been approved under the EU legislative process.
It demanded that Brussels provide assurances the law would allow the sales of new cars with combustion engines that run on synthetic fuels.
While the last-minute block frustrated many EU capitals, Paris had in turn already irked Berlin by insisting on giving nuclear energy a starring role in European plans to produce more green technology in Europe.
Paris and Berlin have traditionally worked together to push forward the EU agenda.
The European Commission, the EU's executive arm, has been holding talks with Germany's transport ministry to resolve the dispute over cars.
Late Thursday commission chief Ursula von der Leyen sounded an optimistic note about the negotiations that were "progressing", but added the issue was not raised during the leaders' talks.
"There is the will on both sides to resolve this topic, and to resolve it within the scope of the provisional agreement," von der Leyen told a press conference.
German Chancellor Olaf Scholz told reporters before the summit that talks were "on the right track".
It is now really only a matter of finding the right way to implement this promise," Scholz said.
Pressure on Germany
Germany, which boasts one of the world's biggest car manufacturing industries, blocked the deal signed last year in a move viewed as a product of domestic politics.
Scholz heads a coalition made up of his social democrats and rival Greens and liberals.
The synthetic fuels Germany wants an exemption for are still under development, produced using low-carbon electricity. The technology is unproven, but German manufacturers hope it will lead to the extended use of combustion engines.
While Germany led the revolt against the combustion engine ban, it is not alone. It has formed a small alliance with countries including Italy, another major car manufacturer, and eastern European states such as Poland and Hungary.
France has not held back from publicly criticising Germany.
Against this tense backdrop, French President Emmanuel Macron will meet Scholz one-on-one Friday.