LONDON — European stocks are expected to open around the flatline on Tuesday as tariff uncertainty causes global markets to waver.

The U.K.'s FTSE index is seen largely unchanged, Germany's DAX and France's CAC 40 are expected to be just a touch into negative territory and Italy's FTSE MIB 0.15% lower.

Regional bourses kicked off the new trading month higher on Monday, with the defense and health-care sectors receiving a boost from corporate news.

The mood has changed overnight, however, with Asia-Pacific markets trading mixed and U.S. stock futures little changed on Monday night, with investors weighing the trade landscape after a U.S. federal appeals court ruled that most of President Donald Trump's global tariffs are illegal.

The U.

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