U.S. stocks dove Tuesday following another stunning reversal, with Wall Street veering from a huge gain at the opening of trading to more losses at the close, because investors still have no idea what to make of President Donald Trump’s trade war, which is scheduled to kick into a higher gear after midnight.

After blasting to an early gain of 4.1%, which would have marked its best day in years, the S&P 500 quickly lost all of it. It then careened to a loss of 3% before paring its drop to 1.6%. That left the index, which sits at the heart of many investors’ 401(k) accounts, nearly 19% below its record set in February.

The Dow Jones industrial average lost 320 points, or 0.8%, after erasing an earlier surge of 1,460 points, while the Nasdaq composite dropped 2.1%.

The deep swings followed rallies for stocks globally earlier in the day, with indexes up 6% in Tokyo, 2.5% in Paris and 1.6% in Shanghai. But even after those jumps, analysts had been warning to expect more swings up and down for financial markets not just in the days ahead but also the hours.

Hope still remains on Wall Street that negotiations may be possible, which helped drive the morning’s rally. Trump said Tuesday that a conversation with South Korea’s acting president helped them reach the “confines and probability of a great DEAL for both countries.”

Japanese stocks led global markets higher after the country’s prime minister, Shigeru Ishiba, appointed his trade negotiator for talks with the United States.

White House press secretary Karoline Leavitt then said Tuesday that Trump’s threats of even higher tariffs on China will become reality after midnight, when imports from China will be taxed at a stunning 104% rate.

On Wall Street, companies with vast supply chains around the world helped lead the losses. Ralph Lauren sank 5.6%, for example. It sourced about 15% of its products from China last fiscal year.

Richfield-based Best Buy doesn’t import many products directly from China, but the electronics industry in general has a supply chain that heavily depends on the country. Best Buy estimates vendor imports from China make up about 55% of the products it purchases, and the retailer’s stock fell 8.3%

On the winning side of Wall Street were health insurers, which rose after the Centers for Medicare & Medicaid Services announced a stronger-than-expected increase in Medicare Advantage payments for next year. Humana jumped 10.7%, and Minnetonka-based UnitedHealth climbed 5.4%.

All told, the S&P 500 lost 79.48 points to 4,982.77. The Dow dropped 320.01 to 37,645.59, and the Nasdaq composite sank 335.35 to 15,267.91.

In the bond market, longer-term Treasury yields rose for a second straight day to recover more of their sharp losses from prior months. The yield on the 10-year Treasury climbed to 4.27% from 4.15% late Monday and from just 4.01% late Friday.

— Associated Pres