Stocks plunged on Friday after President Donald Trump ordered that U.S. manufacturers find alternatives to their operations in China. Apple led the way lower.

The Dow Jones Industrial Average closed 623.34 points lower, or 2.4% at 25,628.90. The S&P 500 slid 2.6% to close at 2,847.11. The Nasdaq Composite dropped 3% to end the day at 7,751.77. The losses brought the Dow's decline for August to more than 4%.

The major indexes also posted weekly losses for the fourth straight time. The Dow dropped about 1% this week while the S&P 500 pulled back 1.4%. The Nasdaq lost 1.8%.

Trump tweeted on Friday: "Our great American companies are hereby ordered to immediately start looking for an alternative to China, including bringing..your companies HOME and making your products in the USA." However, it is not clear how much authority the president has on this front.

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"The threats have always been out there but there's been no need to provoke that," said Art Hogan, chief market strategist at National Securities. "It's almost like the administration was expecting the Fed to announce a rate cut at the Jackson Hole meeting."

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Apple shares dropped 4.6%. The VanEck Vectors Semiconductor ETF (SMH) slid 4.1% as Nvidia and Broadcom both fell around 5%. Caterpillar shares, meanwhile, pulled back 3.3%.

Friday's decline added to a series of sharp moves down this month. The Nasdaq has now fallen at least 1% six times this month while the Dow has posted five drops of 1% or more. The S&P 500 has closed down 1% or more four times in August. Those moves come as the U.S.-China trade war intensifies while the bond market flashes a recession signal.

Trump's tweets come after China unveiled new tariffs on Chinese goods. China will implement new tariffs on another $75 billion worth of U.S. goods, including autos. The tariffs will range between 5% and 10% and will be implemented in two batches on Sept. 1 and Dec. 15.

Earlier in the day, stocks teetered around the flatline after Federal Reserve Chairman Jerome Powell delivered a speech from an annual central banking symposium in Jackson Hole, Wyoming.

In it, he said the Fed will do what it can to sustain the current economic expansion. "Our challenge now is to do what monetary policy can do to sustain the expansion so that the benefits of the strong jobs market extend to more of those still left behind, and so that inflation is centered firmly around 2 percent."

He also noted there is no "rulebook" for the current U.S.-China trade war, adding that "fitting trade policy uncertainty into this framework is a new challenge."

But traders may have wanted a clearer suggestion that the Fed would cut rates in September. The market was looking for a more aggressive walk-back of his now infamous "midcycle adjustment" comment that signaled the July rate cut was just an adjustment and not the start of a trend.