Europe's embattled auto industry and its backers have lobbied hard for Brussels to relax the ban over the past year -- and a decision was expected for Wednesday.

But a commission spokesperson told AFP any announcements would now come on December 16.

The goal of switching all new cars to electric by 2035 was set in 2023 as a flagship measure of the EU's environmental Green Deal and a key step towards the bloc achieving climate neutrality by 2050.

But European automakers have been clamouring for a rethink in the face of fierce competition from China and a slower-than-expected shift to electric vehicles.

German Chancellor Friedrich Merz has emerged as a leading voice in support of car manufacturers, urging Brussels to allow sales of plug-in hybrids, range-extender vehicles and highly efficient combustion engines beyond 2035.

And Italy wants new cars running on biofuels to remain legal after the deadline.

In the opposing camp, France wants to stick as closely as possible to the all-electric trajectory to safeguard massive investments already made by its carmakers.

Road transport accounts for about 20 percent of total planet-warming emissions in Europe, and 61 percent of those come from cars' exhaust pipes, according to the EU.