While the market initially rose slightly, those gains evaporated as the issue of a trade war resurfaced later Friday morning. Peter Navarro, the director of the White House trade office, said on CNN that the United States would increase tariffs on Chinese imports if the two countries could not reach an agreement on trade by the end of a 90-day negotiating period. President Trump and President Xi Jinping of China had agreed on Saturday to the standstill on new tariffs, but confusion about the nature of the agreement has only added to recent volatility in the stock markets based on widespread expectation that the American economy will likely slow next year.

Stocks started the week higher after news of the truce. But after Mr. Trump took to Twitter to threaten China with further tariffs, and then news broke of the arrest of Meng Wanzhou, a top Chinese technology executive, at the behest of the authorities in the United States, markets went into a tailspin. For the week, the S&P 500 is down more than 4 percent.

On Friday, Canadian prosecutors said Ms. Meng, the chief financial officer of Huawei and a daughter of the company’s founder, was charged with fraud. They said Ms. Meng may have personally participated in a scheme to trick American financial institutions into making transactions that violated United States sanctions against Iran.

The arrest could mark a risky new phase for many big technology firms, which depend on networks of factories and subcontractors in Asia and have bet on strong demand from Chinese consumers to fuel future growth.

Shares of these companies fared particularly poorly on Friday. Companies that make networking equipment and cellphones in China were also sharply lower. The semiconductor maker Advanced Micro Devices fell more than 8 percent, while Apple was down more than 3 percent. Microsoft and Amazon both fell more than 4 percent. And the tech-heavy Nasdaq composite index fell more than 3 percent.