Donald Trump, 2016 Republican presidential nominee, speaks during a campaign rally at the Erie Insurance Arena in Erie, Pennsylvania, U.S., on Friday, Aug. 12, 2016.

U.S. actor and producer Robert De Niro said on Saturday that U.S. Republican presidential candidate Donald Trump should not run for president because he was "totally nuts".

Trump, a billionaire businessman seeking his first public office, has courted controversy with a string of inflammatory statements about his main opponent Hillary Clinton, guns, Mexicans, Muslims and war veterans, among others.