Wall Street stocks dropped for the week despite some improving US data as worries ranging from a slowing Chinese economy to the Volkswagen emissions scandal dampened sentiment.
The deepest losses came in the tech-rich Nasdaq Composite Index, which shed 140.73 points (2.92 percent) to 4,686.50.
The Dow Jones Industrial Average dipped 69.91 (0.43 percent) to 16,314.67, while the S&P 500 fell 26.74 (1.37 percent) to 1,931.34.
Analysts said there was no single factor driving the week's losses, but described a broad-based malaise that has stifled buying interest.
"The markets are in a corrective phase," said Mace Blicksilver, director of Marblehead Asset Management, who spotlighted the strengthening dollar as a particular source of anxiety.
Jack Ablin, chief investment officer, at BMO Private Bank, described the market as in a "slow moving correction" as investors reconsider whether high US equity valuations are merited given the sluggish state of the global economy.
A variety of concerns, from the slowdown in China to Volkswagen is "prompting investors to reassess," Ablin said.
Some of the market's feeblest moments followed fresh signs of weakness in China, with a lower Asia region economic forecast from the Asian Development Bank sparking declines on Tuesday and poor Chinese factory data leading to further losses on Wednesday.
The declines coincided with a visit to the US by Chinese President Xi Jinping, who tried to rebuff worries about the world's second biggest economy during meetings with leading US chief executives and politicians.
The week's most closely-watched US economic report came Friday with the Commerce Department reporting US second-quarter growth at a peppy 3.9 percent, up from a prior estimate of 3.7 percent.
The strong growth numbers corroborated remarks from US Federal Reserve Chair Janet Yellen the prior evening that a hike in benchmark interest rates was "likely" by year's end.
Yellen said policy makers will monitor international conditions, but that the US economy appeared on solid footing.
Yellen's comments lifted stock markets early Friday, but the rally fizzled at midday due to weakness in technology and biotechnology stocks.
- Biotechs under fire -
Biotechnology stocks were also in the spotlight after Democratic presidential frontrunner Hillary Clinton pledged to take action against runaway drug price increases following a report spotlighting one medication that rose from $13.50 per pill to $750 after the rights were sold.
"I want to both protect consumers and promote innovation, while putting an end to profiteering," Clinton said.
Dow member Caterpillar announced a major cost-cutting program in response to the downturn in the energy and mining industries. Caterpillar could cut more than 10,000 jobs and close 20 plants by 2018.
On the flip-side, Nike wowed Wall Street by reporting that earnings for the quarter ending August 31 jumped 22.6 percent to $1.2 billion. Nike also reported a 30 percent rise in revenues from China to $886 million.
Aerospace giant Boeing also made China news, announcing a record $38 billion in new orders with Chinese firms during Xi's visit to company plant near Seattle.
Facebook announced that its Instagram photo-sharing platform passed 400 million users. The social network company's Oculus virtual reality hosted a Los Angeles presentation on the technology to software developers.
Goldman Sachs chief executive Lloyd Blankfein announced that he will be treated for lymphoma. Blankfein said he has a curable form of the blood cancer and that the prognosis is good.
Next week's calendar includes US auto sales for September and a heavy schedule of economic indicators, culminating with the monthly jobs report.