WASHINGTON — President Donald Trump placed a 25% tax Monday on goods imported from Japan and South Korea, as well as new tariff rates on Malaysia, Kazakhstan, South Africa, Laos and Myanmar.

Trump provided notice of the tariffs to begin Aug. 1 by posting letters on Truth Social that were addressed to Japanese Prime Minister Shigeru Ishiba and South Korean President Lee Jae-myung. The letters warned both countries to not retaliate by increasing their own import taxes or else the Trump administration would further increase tariffs.

“If for any reason you decide to raise your Tariffs, then, whatever the number you choose to raise them by, will be added onto the 25% that we charge,” Trump wrote.

The letters were not the final word from Trump on tariffs, so much as another episode in a global economic drama in which the president has placed himself at the center. His moves have raised fears that economic growth will slow to a muddle, if not make the U.S. and other nations more vulnerable to a recession. But Trump is confident that tariffs are necessary to bring back domestic manufacturing and fund the tax cuts he signed into law Friday.

Following a now well-worn pattern, Trump plans to continue sharing the letters on social media and then mail them.

The letters are not negotiated settlements but Trump’s own choice on rates, a sign that the closed-door talks with foreign delegations failed to produce satisfactory results for either side. White House press secretary Karoline Leavitt said Trump was, by setting the rates himself, creating “tailor-made trade plans for each and every country on this planet, and that’s what this administration continues to be focused on.”

Wendy Cutler, vice president of the Asia Society Policy Institute who formerly worked in the office of the U.S. Trade Representative, said the tariff hikes on Japan and South Korea are “unfortunate.”

“Both have been close partners on economic security matters and have a lot to offer the United States on priority matters like shipbuilding, semiconductors, critical minerals and energy cooperation,” she said. “Moreover, companies from both countries have made significant manufacturing investments in the U.S. in recent years, bringing high-paying jobs to U.S. workers and benefiting communities all around the country.”

The S&P 500 stock index was down nearly 1% in Monday afternoon trading, while the interest charged on the 10-year U.S. Treasury notes had increased to nearly 4.39%, a figure that could translate into elevated rates for mortgages and auto loans.

Trump has declared an economic emergency to unilaterally impose the taxes, suggesting that they are remedies for past trade deficits. But it’s unclear what he gains strategically against China — another stated reason for the tariffs — by challenging two crucial partners in Asia who could counter China’s economic heft.

“These tariffs may be modified, upward or downward, depending on our relationship with your Country,” Trump wrote in both letters.

Because the new tariff rates go into effect in about three weeks, Trump is setting up a period of possibly tempestuous talks to reach new frameworks.

Trump initially sparked hysteria in the financial markets by announcing tariff rates on dozens of countries, including 24% on Japan and 25% on South Korea. To calm the markets, Trump unveiled a 90-day negotiating period during which goods from most countries were taxed at a baseline 10%.

The 90-day negotiating period technically ends Wednesday, even as multiple administration officials suggested that the three-week period before implementation is akin to overtime for additional talks that could change the rates. Trump planned to sign an executive order Monday to delay the official tariff increases until Aug. 1, Leavitt said.

Administration officials have said Trump is relying on tariff revenues to help offset the tax cuts he signed into law, a move that could shift a greater share of the federal tax burden onto the middle class and poor because importers would likely pass along much of the cost of the tariffs. Trump has warned major retailers to simply “eat” the higher costs, instead of increasing prices in ways that could intensify inflation.

Trump’s team promised 90 deals in 90 days, but his negotiations have produced only two trade frameworks.

His trade framework with Vietnam was clearly designed to box out China from routing its America-bound goods through that country, by doubling the 20% tariff charged on Vietnamese imports on anything traded transnationally.

The quotas in the United Kingdom framework would spare that nation from the higher tariff rates being charged on steel, aluminum and autos, still British goods would generally face a 10% tariff.

According to Trump’s letters, autos would be tariffed separately at the standard 25% worldwide, while steel and aluminum imports would be taxed at 50%. The broader 25% rates on Japan and South Korea would apply to goods not already covered by the specific sectoral tariffs.

Trump has also said on social media that countries aligned with the policy goals of BRICS — an organization composed of Brazil, Russia, India, China, South Africa, Egypt, Ethiopia, Indonesia, Iran and the United Arab Emirates — would face additional tariffs of 10%.