China has been embroiled in a months-long trade war with US. (File)

US President Donald Trump said the European Union is less fair to the United States on trade than even China, which is embroiled in a months-long trade war with Washington.

"The European Union treats us, I would say, worse than China, they're just smaller," Trump told a gathering of real estate agents in Washington.

Trump on Friday declared that some imported vehicles and parts pose a national security threat but delayed a decision for as long as six months on whether to impose tariffs to allow for more time for trade talks with the European Union and Japan.