President Trump is telling some of the nation’s largest companies that they should eat the cost of his tariffs, as a growing number of businesses signal that they must raise prices to blunt the impact of a persistent global trade war.

As a result, the man who ran for the presidency by boasting about his business acumen is now openly sparring with corporate America, seeking to dictate how Walmart, Mattel, and other retailers and manufacturers respond to some of the highest levies seen in decades.

Since the spring, the United States has imposed a 10 percent tariff on nearly every nation, with steeper duties reserved for specific products and countries, including a minimum 30 percent tax on Chinese imports.

While the White House insists the president’s strategy is working — generating new revenue and forcing nations to negotiate — some companies have started to report early signs of financial strain. Their warnings have affirmed economists’ long and widely held belief that tariffs fall hardest on U.S. companies and consumers, not the allies and adversaries that Mr. Trump seeks to punish.

But the White House repeatedly has dismissed this evidence, while the president himself has increasingly needled companies for trying to ameliorate the financial fallout.

“He maintains the position that foreign countries absorb these tariffs,” Karoline Leavitt, the White House press secretary, told reporters at a briefing on Monday.