President Donald Trump speaks with the news media before boarding Marine One for travel to Europe from the White House, in Washington, July 10, 2018.

President Donald Trump said Tuesday night that the U.S. would slap a 25 percent tariff on cars coming from the European Union.

The president's statement came hours after The Wall Street Journal reported that Commerce Secretary Wilbur Ross said he had postponed an August timeline to publish a report on auto tariffs.

"We're going to put a 25 percent tax on every car that comes into the United States from the European Union," Trump said at a campaign rally in West Virginia.

Ross told The Journal that it wasn't clear that a report on potential tariffs would come out by the end of August. The Commerce secretary also declined to set a new timeline, according to the newspaper. He said the report was being delayed because of ongoing negotiations with Mexico, Canada, and the European Commission.