Disputes between France and Germany over the future of nuclear energy and the long-term acceptability of fossil fuel engines risk spilling over into a gathering of the 27 European Union leaders in Brussels on Thursday.
There are two bones of contention between the EU's largest economies: petrol engines and nuclear power plants.
Earlier this month, Berlin blocked a European deal which would have banned the sale of vehicles with combustion engines from 2035.
The ban is key to Brussels' plan to become a climate neutral economy by 2050, with net-zero greenhouse gas emissions.
Germany intervened after the car ban had been approved under the EU legislative process. Berlin demanded that Brussels agree that the law would allow the sales of new cars with combustion engines that run on synthetic fuels.
While Germany led the revolt against the combustion engine ban, it is not alone. It has formed an alliance with Italy, another major car manufacturer, and eastern European states such as Poland and Hungary.
Nuclear power struggle
France has, meanwhile, irked Germany by giving increasing prominence to nuclear power in European plans for the generation of electricity.
Germany is committed to a complete shutdown of its three remaining nuclear reactors once the energy crisis provoked by the Russian invasion of Ukraine has been resolved.
The European Commission's plans for the sector, announced earlier this month, exclude all current forms of atomic energy except so-called fourth-generation reactors based on technology that has proved difficult to install and is still under development.
This potential EU ban on reactors now in use poses a major economic headache for the French who depend on ageing nuclear plants for nearly three-quarters of their electricity.
President Macron has promised to "focus on the role of nuclear in decarbonisation" during the leaders' meeting.
The official agenda for Thursday's summit includes EU support for Ukraine and boosting economic competitiveness in the face of threats from US and Chinese subsidised producers.