President Donald Trump on Monday set a 25% tax on goods imported from Japan and South Korea, as well as new tariff rates on a dozen other countries.

In letters so far to 14 countries, including smaller exporters to the United States such as Serbia, Thailand and Tunisia, Trump hinted at opportunities for additional negotiations, even while warning that reprisals would draw a like-for-like response.

The country’s new president, in office for a little over a month, had just dispatched his senior deputies to Washington to try to work out a trade deal.

While South Korean imports to the U.S. face 25% tariffs, the same as Trump promised in April, the rate on Japan has been raised by 1 percentage point to 25%.

Japan and South Korea, the United States’ closest security allies in Asia and key partners in its effort to counter China, were sent scrambling Tuesday after the U.S. president renewed his threat to impose steep tariffs on their goods,

It shows that personal grudges rather than simple economics are a driving force in the U.S. leader’s use of tariffs.

South Korea said it will review regulations flagged by the US while pressing for an easing of sectoral tariffs after President Donald Trump sent a letter with a new August deadline for imposing 25% across-the-board levies.

The U.S. will put in place a 25% tariffs on imports from Japan and South Korea starting on Aug. 1, according to letters posted by President Donald Trump on his social media platform on Monday. Trump wrote to Japanese Prime Minister Shigeru Ishiba and South Korean President Lee Jae-myung to inform them of the news, citing unfair trade balances.

Donald Trump said South Korea should pay for its own defence as he ramped up pressure on the Asian ally ahead of the imposition of a 25 per cent tariff on imports from the country.The president said it was “very unfair” that the US was paying for the defence of a successful country,

U.S. President Donald Trump's latest tariff delay provided some hope to major trade partners Japan, South Korea and the European Union that deals to ease duties could still be reached, while bewildering some smaller exporters such as South Africa and leaving companies with no clarity on the path forward.