Key global stock markets tumbled upon opening on Monday as the world’s reaction to President Donald Trump’s tariffs campaign continued — and as U.S. futures signaled more turmoil for American markets.

In the U.S., Dow Jones futures were down about 1,200 points or 3.33% on Monday morning. S&P 500 and NASDAQ futures were down about 3.5%. A drop of 7% on the S&P 500 before 3:35pm ET will trigger a market-wide circuit breaker that will halt trading for 15 minutes.

Hong Kong leads Asian slide

Tokyo’s Nikkei 225 index lost nearly 9% shortly after the market opened on Monday, the steep decline triggering a circuit breaker that temporarily halted trading. Japan’s broader TOPIX index sank 8%.

In Taiwan, the Taiex lost 9.7%, while in Singapore the STI fell more than 8%.

South Korea’s KOSPI index fell more than 5.5% in Monday trading, with Australia’s S&P/ASX 200 sliding more than 6% before recovering slightly.

Hong Kong’s Hang Seng Index dropped 13.22% — its worst one-day performance since 1997 during the Asian Financial Crisis — with Chinese tech stocks like Alibaba and Baidu among the big losers.

On the mainland — where there are fewer international investors — the Shanghai Composite Index dropped more than 7%, despite being buoyed by state-owned investors known as the “National Team.”

India’s stock markets also struggled. The BSE’s Sensex dropped 5.19% while the broader Nifty tumbled 5%.

Asian markets collectively posted their worst day trading session since 2008.

Europe joins rout

European indexes followed suit on Monday morning.

The British FTSE 100 index fell 6% upon opening, while the pan-European Stoxx 600 index dropped more than 6%.

Germany’s DAX index fell 10%, France’s CAC lost 6.6% and Italy’s FTSE MIB slid 5.7%.

US braced for more losses

Investors are bracing for continued market turmoil on Monday in response to Trump’s “Liberation Day” tariffs announced last week.

Speaking with reporters on Air Force One on Sunday, Trump addressed the recent market turbulence and subsequent fears of an imminent recession.

“Now what’s going to happen with the market? I can’t tell you, but I can tell you, our country has gotten a lot stronger, and eventually it’ll be a country like no other, it’ll be the most dominant country economically in the world,” Trump said.

“I don’t want anything to go down, but sometimes you have to take medicine to fix something and we have such a horrible — we have been treated so badly by other countries because we had stupid leadership that allowed this to happen,” the president added.

U.S. markets closed significantly down on Friday. The Dow Jones Industrial Average plummeted 2,230 points, or 5.5%, while the S&P 500 plunged 6%.

The tech-heavy Nasdaq declined 5.8%. The decline put the Nasdaq into bear market territory, meaning the index has fallen more than 20% from its recent peak.

The trading session on Friday marked the worst day for U.S. stocks since 2020. The second-worst day for U.S. stocks since 2020 happened on Thursday, a day earlier.

ABC News’ Ellie Kaufman, Karson Yiu, Zunaira Zaki, Max Zahn and Hannah Demissie contributed to this report.