The heads of Germany's big three automakers met the US ambassador on Wednesday to reaffirm their support for zero tariffs on EU-US trade in cars as they step up lobbying efforts to avert a trade war.

Two industry sources briefed on the talks said the chiefs of BMW, Volkswagen and Mercedes-parent Daimler met with Richard Grenell and said they would support the elimination of EU tariffs on cars imported from the US provided the US did the same — and dropped its present threat to increase them.

The German car bosses also said they could issue a pledge to maintain levels of investment in the US, provided a tariff spiral were averted. Such a pledge in fact carries an implicit threat to shift production out of the US if the Trump administration ramps up tariffs on car imports from the EU.