Stocks around the world tumbled Monday as investors braced for a week of market tumult caused by the expected announcement of yet more tariffs by President Trump on America’s biggest trading partners.

Since taking office a little over two months ago, Mr. Trump has kept investors and companies guessing with a haphazard rollout of what he calls an “America First” trade policy. He has threatened, imposed and in some cases then paused the start of new tariffs on goods coming into the United States.

On Monday, stocks in Japan and Taiwan fell more than 4 percent, while share prices in South Korea were down 3 percent. The Nikkei 225 index in Japan fell into a correction, down 12 percent from its high in late December. Technology companies were hit hard: Chipmakers Taiwan Semiconductor Manufacturing Company, SK Hynix, Samsung and Tokyo Electron recorded declines.

Losses in China were more muted. Hong Kong stocks dropped more than 1 percent and those in mainland China were about 0.5 percent lower. Mainland stocks got some support from a report signaling that China’s export-led industrial sector continues to expand despite Mr. Trump’s initial tariffs.

Markets in Europe slumped, with the Stoxx 600 index falling 1.8 percent. German automakers, which are particularly exposed to U.S. tariffs, extended recent losses: Volkswagen, Europe’s largest carmaker, fell more than 4 percent in Frankfurt.

Futures on the S&P 500, which allow investors to trade the benchmark index before exchanges open in New York, indicated a decline of about 1 percent. On Friday, the S&P 500 dropped 2 percent on concerns that Mr. Trump’s tariffs could recharge inflation and dampen consumer sentiment, dragging the index down to a fifth weekly fall in the past six weeks.

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