President Trump’s tariffs are already taking a toll on China’s factories.

Three weeks into a trade war that pushed import tariffs of Chinese-made goods to 145 percent, an official report on manufacturing activity signaled that in April, Chinese factories experienced the sharpest monthly slowdown in more than a year.

The report, a survey of industrial firms published on Wednesday by the National Bureau of Statistics, provides the first official indication of how the U.S. tariffs are affecting the Chinese economy. China has responded to the U.S. tariffs with 125 percent tariffs of its own on American goods.

The trade brinkmanship threatens U.S. and Chinese growth — and potentially the global economy. Emerging signs of hardship in both countries have ratcheted up pressure on President Trump and Xi Jinping, China’s top leader, to strike a deal to break the impasse.

Neither Beijing nor Washington appears ready to blink. China’s foreign ministry released a video on Tuesday, saying that the country refuses to cave to “a bully.” President Trump, in an interview with ABC News on Tuesday, continued to push back, saying China was “ripping us off like nobody’s ever ripped us off.” He said he believed that China “probably will eat those tariffs,” defying anxiety among consumers and businesses about the impact of the import taxes he has imposed.

On Tuesday, the shipping giant United Parcel Service announced it would cut 20,000 jobs and close 73 buildings this year. General Motors said it could no longer stand by its previous forecast for solid profit growth this year, citing Mr. Trump’s tariffs on imported cars and imported parts. U.S. consumer confidence fell to its lowest levels in five years.

China’s manufacturing purchasing managers’ index fell to 49.0 in April, down from 50.5 in March. A reading below 50 indicates a deterioration in activity in the sector. The index was above 50 in the previous two months, driven by a bump in orders ahead of the tariffs. The April figure was below what economists had expected.