By Jeff Mason, Bart H. Meijer and David Brunnstrom WASHINGTON/BRUSSELS (Reuters) -U.S. President Donald Trump opened a new phase on Monday in the trade war he launched this year, telling partners, from powerhouse suppliers such as Japan and South Korea to minor players,

President Donald Trump issued separate letters to the president of South Korea and Japan's prime minister on Monday, saying the U.S. will start charging a 25% tariff on Aug. 1. He also sent letters to 12 other countries.