Spain’s Prime Minister Pedro Sanchez has urged the European Commission not to weaken the bloc's 2035 ban on new CO2-emitting cars, a letter seen by Reuters showed, as Brussels readies proposals to potentially roll back the policy.

A leading German EU lawmaker on Friday the Commission will move next week to water down the policy, which would effectively ban new combustion engine cars from 2035 by requiring all cars sold after that date to have zero CO2 emissions. Governments, including Germany and Italy, have pressured the EU to weaken the 2035 ban, arguing this would protect automakers struggling with tough competition from China.

In a letter to European Commission President Ursula von der Leyen, dated Thursday, Sanchez said weakening the policy would risk jobs and factory closures by undermining Europe's attempts to transform its car industry into a powerhouse for manufacturing electric vehicles.

"Any additional relaxation (of the policy) would risk triggering a significant delay in modernization investments, linked to a temporary slowdown in electric vehicle demand," the letter said.

"We therefore reject that combustion vehicles or other technologies without proven viability could continue to be marketed beyond 2035," it said.

Sanchez also called for a "green steel label" to reward auto manufacturers for using low-carbon materials, and a mandatory minimum share of EU-manufactured content in cars.

The Commission is due to make an announcement on the policy on Tuesday.

Manfred Weber, president of the largest lawmaker group in the European Parliament, the EPP, suggested this week the Commission would propose weakening the target to a 90% reduction in CO2 emissions for automakers' fleet targets for 2035.

The planned ban is a key part of the EU's strategy to drive the continent’s decarbonisation and boost the development of electric vehicles.

Automakers, including Mercedes-Benz and BMW, have urged the EU to weaken the policy, amid slower-than-expected electric car sales.

Sweden's Volvo Cars and others say they have already heavily invested in the transition to electric, and any reversal on the ban would be a betrayal.