Wall Street's main indexes ended little changed in choppy trading on Wednesday after Federal Reserve Chair Jerome Powell spoke to the central bank's aim to bring down inflation.

After opening lower, major U.S. indexes had erased losses following Powell's testimony before a Senate committee. He said the Fed is "strongly committed" to bringing down inflation that is running at a 40-year high while policymakers are not trying to cause a recession in the process.

Investors are trying to assess how far stocks can fall as they weigh risks to the economy with the Fed hiking rates to tamp down surging inflation. The S&P 500 earlier this month fell over 20% from its January all-time high, confirming the common definition of a bear market, with the benchmark index last week logging its biggest weekly percentage drop since March 2020.

"Markets continue to be volatile," said said King Lip, chief strategist at Baker Avenue Asset Management in San Francisco. "Certainly we are not out of the woods yet... The concerns are still there."

According to preliminary data, the S&P 500 lost 6.65 points, or 0.18%, to end at 3,758.14 points, while the Nasdaq Composite lost 16.90 points, or 0.15%, to 11,052.41. The Dow Jones Industrial Average fell 54.14 points, or 0.18%, to 30,476.11.

Defensive areas real estate, healthcare and utilities were among the top-gaining S&P 500 sectors.

The energy sector, which has been a strong performer this year, fell along with oil prices.

In company news, Moderna Inc shares rose after the company said an updated version of its COVID-19 vaccine generated a strong immune response against fast-spreading Omicron subvariants.

Dow Inc shares slid after Credit Suisse downgraded the chemicals maker's stock to "underperform."