The Dow Jones Industrial Average increased 44.44 points, or 0.13 percent, to 34,933.23. The S&P 500 was up 5.09 points, or 0.12 percent, to 4,374.30. The Nasdaq Composite Index was down 32.70 points, or 0.22 percent, to 14,644.95.
Six of the 11 primary S&P 500 sectors ended in red, with energy down 2.94 percent, leading the laggards. Consumer staples rose 0.92 percent, the best-performing group.
U.S.-listed Chinese companies traded mostly lower with eight of the top 10 stocks by weight in the S&P U.S. Listed China 50 index ending the day on a downbeat note.
Powell started his two-day testimony at U.S. Congress on Wednesday on the state of the U.S. economy. In prepared remarks released ahead of the testimony, the Fed chief said he still expects inflation to moderate.
"Inflation has increased notably and will likely remain elevated in coming months before moderating," he said, adding, "inflation is being temporarily boosted by base effects."
Powell noted that the labor market, although improving, "is still a long way to go" toward recovering from the pandemic.
He also said that the U.S. economy is "still a ways off" from the progress that the Fed wants to see before tapering the central bank's asset purchases.
The Fed has pledged to keep its benchmark interest rates unchanged at the record-low level of near zero, while continuing its asset purchase program at least at the current pace of 120 billion U.S. dollars per month until the economic recovery makes "substantial further progress."
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