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,

Donald Trump has warned 14 countries—mostly in Asia—that steep new tariffs will begin August 1 unless fresh trade deals are struck, reigniting tensions with key US partners like Japan, South Korea, and Thailand.

President Trump on Monday posted a barrage of letters he sent to country leaders, saying he would impose an array of tariffs similar to levels he announced in April. The most significant were letters to the leaders of Japan and South Korea that informed them of 25% tariffs on imports from their respective countries.