» Stocks skid on worries of a prolonged trade war with China.

Heightened worries that the U.S. and China are headed for a long standoff in their costly trade dispute put investors in a selling mood Thursday.

Stocks ended sharply lower on Wall Street in a broad sell-off that left the benchmark S&P 500 index on track for its third straight weekly loss and had the Dow Jones Industrial Average down more than 400 points until late afternoon.

Traders sought safety in the bond market, driving bond prices higher. This pulled the yield on the 10year Treasury to 2.31 percent, its lowest level in more than a year.

The stock market has been highly volatile since Washington and Beijing escalated their dispute over trade this month. Now, the two sides have broken off negotiations and appear set for a long standoff. Investors are concerned that a prolonged trade war could stunt economic growth and hurt corporate profits.

“Markets are appreciating how far apart the two sides are and how messy the grand deal would be that both sides had led us to believe was coming very quickly,” said Sameer Samana, senior global market strategist at the Wells Fargo Investment Institute.

The S&P 500 index fell 34.03 points, or 1.2 percent, to 2,822.24. The index was down 2.5 percent before the selling eased. The Dow lost 286.14 points, or 1.1 percent, to close at 25,490.47. At its lowest, the Dow slid 448 points.

The Nasdaq composite dropped 122.56 points, or 1.6 percent, to close at 7,628.28. The Russell 2000 index of small company stocks gave up 30.25 points, or 2 percent, to close at 1,501.38.

Markets in Asia and Europe also saw steep losses.

The U.S. and China concluded their 11th round of trade talks this month with no agreement. Instead, the U.S. moved to increase tariffs on Chinese goods, prompting China to reciprocate. The dispute escalated further after the U.S. proposed restrictions on technology sales to China, though it has temporarily backed off.

Both the U.S. and China have made overtures about continuing trade talks, but none are scheduled. That uncertainty has many traders nervous about how and when the dispute will be resolved.

“Now people are realizing how weighty the issue is and how many different aspects of it are just so intractable, where it’s going to be difficult for the Chinese side to give in and it’s going to be hard for the U.S. not to ask for some of these changes,” Samana said.

Banks also took heavy losses in the sell-off as bond yields fell sharply. Lower yields mean lower interest rates on loans, which makes lending less profitable. JPMorgan dropped 2 percent,and Bank of America slid 2.6 percent.

Gold climbed 0.9 percent to $1,285.40 per ounce, silver jumped 1.1 percent to $14.61 per ounce and copper rose 0.1 percent to $2.68 per pound.

The dollar fell to 109.49 Japanese yen from 110.29. The euro strengthened to $1.1183 from $1.1160.