All three major U.S. stock indexes gyrated wildly in the final minutes of a session that ended with the Dow joining the S&P in negative territory and the Nasdaq eking out a nominal gain.

The indexes enjoyed a brief surge after the Federal Open Markets Committee left key interest rates near zero. But those gains quickly evaporated as the Fed statement warned it would soon begin raising the Fed Funds target rate to combat persistent inflation related to the COVID-hobbled supply chain.

"With inflation well above 2 percent and a strong labor market, the Committee expects it will soon be appropriate to raise the target range for the federal funds rate," the statement said.

Stocks slid into negative territory once Fed Chairman Jerome Powell's subsequent Q&A got under way, during which he warned that inflation remains above its long-run goal and supply problems are bigger and more long-lasting than previously thought.

"When reporters asked Powell if the Fed would consider raising rates at every meeting, which would mean more than four times this year, he didn't say they wouldn't, which indicates a flexibility to raise rates much more quickly (if necessary) than anyone was expecting," said Chris Zaccarelli, chief investment officer at Independent Advisor Alliance in Charlotte, North Carolina.

The Dow Jones Industrial Average fell 129.64 points, or 0.38%, to 34,168.09, the S&P 500 lost 6.52 points, or 0.15%, to 4,349.93 and the Nasdaq Composite added 2.82 points, or 0.02%, to 13,542.12.

While all 11 major sectors of the S&P 500 spent much of the trading day green, by the time the dust settled only tech and financials showed gains.

Fourth-quarter reporting season has hit full stride, with one-fifth of the companies in the S&P 500 having posted results. Of those, 81% have beaten consensus, according to Refinitiv data.

Microsoft Corp gained 2.8% after current-quarter revenue guidance, driven in part by its cloud business, came in above consensus.

Boeing Co was down 4.8% after the plane maker said it incurred $4.5 billion in charges in the fourth quarter related to its sidelined 787.

Toy maker Mattel Inc jumped 4.3% after regaining the right from rival Hasbro Inc to produce toys based on Walt Disney Co's "Frozen" franchise.

Shares of Tesla fell about 5% in extended trade after the electric vehicle maker warned that its factories would run below capacity through 2022 due to supply-chain limitations.

Declining issues outnumbered advancing ones on the NYSE by a 2.12-to-1 ratio; on Nasdaq, a 1.98-to-1 ratio favored decliners.

The S&P 500 posted 12 new 52-week highs and 9 new lows; the Nasdaq Composite recorded 28 new highs and 206 new lows.

Volume on U.S. exchanges was 14.50 billion shares, compared with the 11.58 billion average over the last 20 trading days.

(Reporting by Stephen Culp in New York; Additional reporting by Sinead Carew in New York; Noel Randewich in Oakland, Calif.; and Susan Mathew, Devik Jain and Bansari Mayur Kamdar in Bengaluru; Editing by Matthew Lewis)

By Stephen Culp