The Audi PB 18 e-tron is on display at the Auto show in Paris, France, Tuesday, Oct. 2, 2018, 2018. (Photo: AP)

The European Union (EU) said on Monday that it will have a "swift and adequate" reaction should the United States decide to impose import duties on European cars and auto parts on the grounds of national security threat.

The US Commerce Department on Sunday submitted to the White House the results of its investigation into the effects of imports of automobiles and automobile parts on the US national security.

"Were this report translated into action detrimental to European exports, the European Commission would react in a swift and adequate manner," said Margaritis Schinas, a spokesman for the European Commission, at a news briefing in Brussels.

US President Donald Trump has 90 days to decide whether to adopt the recommendations and introduce tariffs on imported vehicles and auto parts, including those from Europe.