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 has officially delayed imposing higher tariffs on US imports, while sending letters to 14 countries including Japan and South Korea detailing the levies they face. The latest development comes as a 90-day pause the White House placed on some of its most aggressive import taxes was set to expire this week.

President Donald Trump's latest executive order delaying official tariff increases on dozens of countries until Aug. 1 has relieved some pressure on world markets, but he also ordered a 25% tax on goods imported from Japan and South Korea,

Japanese Prime Minister Shigeru Ishiba called the announcement of slightly higher US tariffs “truly regrettable” while he vowed to continue to protect his nation’s interests in the extended trade negotiations.

Japan's trade deal with the U.S. must include tariff concessions for its vital automobile industry, top trade negotiator Ryosei Akazawa said on Tuesday, after President Donald Trump announced 25% tariffs on goods from Japan starting August 1.