By Jeff Mason and Leika Kihara WASHINGTON/TOKYO (Reuters) -Powerhouse Asian economies Japan and South Korea said on Tuesday they would try to negotiate with the U.S. to soften the impact of sharply higher tariffs that President Donald Trump now plans to impose from the start of August.

President Donald Trump on July 7 threatened to impose 25 percent tariffs on Japan and South Korea, and levies as high as 40 percent on 12 other countries, if they did not reach a deal by August 1.

President Donald Trump on Monday placed a 25% tax on goods imported from Japan and South Korea, citing persistent trade imbalances with the two crucial U.S. allies in Asia