U.S. retailers and manufacturers, faced with sky-high tariffs on Chinese goods, are pausing and reducing shipments from China. The pullback is expected to hit West Coast ports within days.

The number of containers scheduled to arrive at the Port of Los Angeles is anticipated to drop more than 35 percent next week compared with the same period last year, data from the port shows. And a quarter of the ships that had been scheduled for May have canceled because of light volume, said Gene Seroka, the port’s executive director.

Mr. Seroka attributed the expected downturn to President Trump’s tariffs — most notably, tariffs on Chinese goods, many of which will be subjected to levies of up to 145 percent.

The Port of Los Angeles, which handles the largest volume of container shipments from China, reported a surge of imports in recent months as companies tried to get ahead of the tariffs Mr. Trump had long promised. This month, as Mr. Trump’s trade war with China escalated and retailers’ fears about broad tariffs came to fruition, large importers started to scale back their shipments, Mr. Seroka said.

Some of the 125,000 importing companies that rely on the Port of Los Angeles, including big box retailers and home improvement stores, have halted nearly all of their imports from China, he added, referring to conversations with the firms.

“Now, major importers are saying, ‘I’m going to wait, hit the pause button,’” Mr. Seroka said. “I don’t see any quick change.”