Once in office, Mr. Trump muted such talk while embracing its president, Xi Jinping, as a critical ally in the bid to contain North Korea.

But Mr. Trump grew frustrated by China’s reluctance to deprive North Korea of support. His administration let it be known that it would soon unleash tariffs on steel aimed at constraining China’s massive sales of cheap product on world markets. That has yet to happen.

Such tariffs would hurt other exporters of steel, including South Korea and Japan — two American allies. The tariffs would increase steel prices for American automakers.

Some members of the Trump administration continue to attack China as a menace to American prosperity. In a speech delivered earlier this month in Washington, Robert E. Lighthizer, the United States trade representative, called China “a threat to the world trading system that is unprecedented.”

Faced with such an enemy, one might imagine the United States would gather allies in a concerted effort to contain China’s mercantilist ambitions. Except that Mr. Trump, in one of his earliest actions, revoked American participation in the Trans-Pacific Partnership, a pact promoted by his predecessor as a means of doing precisely that. He walked away while extracting no discernible benefits from China.

The decision on the Canadian airplane maker, Bombardier, may imperil a deal on which Mr. Trump has broadcast conflicting intentions — the North American Free Trade Agreement, the landmark pact spanning Canada, the United States and Mexico.

After initially vowing to abandon the deal, Mr. Trump opted to instead renegotiate it. Those talks continue with as yet no signs of meaningful progress.