A mounting dispute between France and Germany over nuclear energy and internal combustion engines poses a possibility of escalating during a meeting of the 27 leaders of the European Union on Thursday.

Two of the largest economies in the European Union got into a spat when Berlin angered several of its allies, including France, by abruptly opposing a historic agreement to ban the sale of new fossil fuel vehicles starting in 2035.

The ban is key to Brussels' ambitious aim to achieve net-zero greenhouse gas emissions by 2050 and become a "climate neutral" economy.

This month, Germany intervened in an unusual move after the EU legislative process had already approved the car ban. Brussels was compelled to guarantee that the bill will permit the sale of new cars with combustion engines that use synthetic fuels.

While the last-minute obstruction annoyed France, Berlin was irritated by Paris' insistence that nuclear energy be given more weight in EU measures to increase the production of green technologies in Europe.

The EU agenda has always been advanced through cooperation between Paris and Berlin. Nonetheless, the division looms over the summit as the leaders gather to talk about EU support for Ukraine and how to increase economic competitiveness in the face of threats mainly from US subsidies.

Despite the fact that no agreement has yet been achieved, EU diplomats believe a different proposal may come in the next few days.

The big picture 

Germany, which has one of the largest automobile manufacturing sectors in the world, vetoed the agreement last year in a move that was seen as the result of local politics. Olaf Scholz, the German Chancellor, leads a coalition of social democrats opposing liberals and Greens.

"It is above all a German affair and an internal debate in German politics that has reached Europe," a senior EU diplomat complained.

"It's not a good look to return to a debate when the European Parliament and European Council have agreed a deal. We cannot run things like this," the diplomat added.

Germany seeks an exemption for the synthetic fuels that are still being developed and generated with low-carbon power. German manufacturers are hoping that despite the technology's lack of experience, it will enable the continued use of combustion engines.

Germany wasn't the only country to rebel against the prohibition on combustion engines. It has forged a modest alliance with nations like Italy, home to yet another big automaker, as well as nations in Eastern Europe like Poland and Hungary.

France has not shied away from criticizing Germany specifically.

Earlier this month, French Transport Minister Clement Beaune blamed his German counterpart for leading "a revolt" against the ban on new petrol- or diesel-engine cars.

Against this tense backdrop, French President Emmanuel Macron will meet with Scholz one-on-one on Friday. 

Another sticking point they will have to work out is France's insistence that the EU acknowledge nuclear power's contribution to Europe's green future.

While nuclear-powered France's request for atomic energy to be put on the list was denied, it did score a minor win.

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