Donald Trump has been tough on American companies that have moved jobs to other countries. That hasn't stopped the presumptive Republican presidential nominee from investing in them.

Trump has denounced units of United Technologies Corp., Ford Motor Co. and Mondelez International Inc. on the campaign trail — and has received income of as much as $75,000 from bonds issued by all three since January 2015, according to his latest financial disclosure form released Tuesday. He also has invested in Apple Inc.'s stock and bonds even though in February he called for a boycott of the company for refusing to help the Federal Bureau of Investigation unlock an iPhone used by a terrorist in San Bernardino, California.

Trump's attacks on U.S. companies reflect a key element of his strategy for winning the White House: to compete against a Democratic rival in Rust Belt states such as Michigan, Wisconsin and Pennsylvania, where working-class voters have been harmed by international trade deals, he's promising to stop the movement of manufacturing jobs overseas.