As financial markets recoiled for a second day and China said that it would hit the United States with its own punishing tariffs, President Trump on Friday sounded a defiant note about his approach, promising that “MY POLICIES WILL NEVER CHANGE.”

Instead, Mr. Trump maintained in a series of posts on Truth Social that his economic strategy is working, as he held up a better-than-expected new jobs report — reflecting hiring before he announced his latest round of tariffs — as a sign the economy remains strong.

Global markets told a different story, as major U.S. indexes slipped into the red hours after China announced new retaliatory tariffs on the United States, signaling a wider trade war. The S&P 500 fell about 2.5 percent, on the heels of its worst day since 2020.

China’s new 34 percent tariffs on American goods are set to take effect next week, matching Mr. Trump’s decision to hit Chinese imports with a 34 percent tariff. The president plans to start imposing an across-the-board 10 percent duty on all of the country’s trading partners on Saturday, followed by additional levies later in the week on China and other nations that he has accused of engaging in unfair trade practices.

The expansive tariffs have set off a global frenzy, as other governments try to figure out how, or if, to retaliate, while trying to persuade Washington to relax its coming taxes on imports. The Trump administration has sent mixed signals over its willingness to negotiate: Some of Mr. Trump’s advisers have said they do not intend to haggle, but the president himself told reporters Thursday that he could make a deal if the United States received something “phenomenal.”

In the midst of the uncertainty, Mr. Trump took to Truth Social, where he circulated another user’s video that argued “Trump is purposely CRASHING the market,” in a bid to force the Federal Reserve to lower interest rates.

He followed up by doubling down on his tariffs, heralding that the United States had already attracted new foreign investment: “THIS IS A GREAT TIME TO GET RICH, RICHER THAN EVER BEFORE!!!”

Turning his attention to China, the president said the country had “PLAYED IT WRONG” by retaliating against the United States. The president and his aides previously have signaled they could ratchet up their tariff rates if other nations reacted similarly.

And Mr. Trump celebrated newly released data on Friday that showed employers added 228,000 jobs last month, more than analysts had anticipated. The president said it showed his strategy was “ALREADY WORKING,” even though the report reflected hiring in the month before the White House announced its new, expansive tariffs.

“HANG TOUGH, WE CAN’T LOSE!!!” he wrote.