When the stock exchange closed on Thursday, the broad S&P 500 index had fallen 0.4 percent, while the technology-heavy Nasdaq's composite index and the Dow Jones industrial index both fell 0.3 percent.
It was the fifth trading day in a row on minus for S&P 500 – the longest decline since January, according to the news agency Bloomberg.
Retail giant Walmart fell 4.5 percent after a quarterly report that was not well received.
Six of the very index-heavy so-called "magnificent seven" companies – e-commerce giant Amazon, iPhone manufacturer Apple, Facebook's parent company Meta, software company Microsoft, semiconductor giant Nvidia, and electric car company Tesla – closed Thursday in negative territory.
The seventh, Google owner Alphabet, rose 0.2 percent.
On Wednesday, all seven fell.
The cautious reluctance to take risks is largely explained by the fact that Federal Reserve Chairman Powell will speak at a meeting in Jackson Hole on Friday – and possibly say something about the direction of interest rates ahead.
Stock valuations are very high right now ahead of Jackson Hole, and investors have very high expectations that Powell will indicate an interest rate cut in September, says Rick Gardner, investment manager at financial advisory firm RGA Investments, to CNBC.
