BERLIN — Even as showrooms in Europe prepare for the arrival of 2014 vehicles, authorities in France have sparked controversy with a drastic action: blocking the registration — effectively shutting down sales — of some popular new Mercedes-Benz cars, including the A-Class, B-Class, CLA and SL models.

The French environment ministry ordered the ban in response to the German carmaker’s defiance of a European Union regulation on the refrigerants permitted in automotive air-conditioning systems, and the ministry says that it won’t back down until Daimler, the parent of Mercedes, complies. The European Union, though supportive of France’s position, has agreed to step in and referee to keep the squabble from spreading.

Why such an uproar over a matter as arcane as an air-conditioning refrigerant?

The ban on registrations was put in place after Mercedes refused to switch to a refrigerant compound that is considerably more climate-friendly than the one currently used in almost all car air-conditioning systems. Mercedes contends that in its crash tests and other independent safety research, the replacement material was flammable in cases where it leaked onto hot engine parts, and that it produced a dangerous gas when burned — increasing the potential harm to passengers in an accident.

European regulators have agreed to review the German test results as part of the process of resolving the tiff. Because of the safety concerns, Germany’s Federal Motor Transport Authority approved the new models for sale with the current refrigerant, a position that escalated the matter from a disagreement over technology to a political dispute.