Fed Chair Jerome Powell said policy makers would proceed carefully although they were not yet confident financial conditions were restrictive enough to get inflation as low as the central bank would like.

Trading was choppy at the start of Powell's press conference but the major equity indexes started to regain some lost ground after about 20 minutes.

This was because the Fed's top official didn't sound as "definitively hawkish" as he had in previous press conferences, according to Michael James, managing director of equity trading at Wedbush Securities in Los Angeles.

"He wasn't as assertive about higher-for-longer, as he has been in the past. That's one takeaway bulls will be focused on, even though he indicated the Fed still has a ways to go to get to its 2% target," said James.

According to preliminary data, the S&P 500 gained 43.80 points, or 1.04%, to end at 4,237.60 points, while the Nasdaq Composite gained 210.23 points, or 1.64%, to 13,061.47. The Dow Jones Industrial Average rose 223.06 points, or 0.67%, to 33,275.93.

Ellen Hazen, chief market strategist at F.L.Putnam Investment Management in Wellesley, Massachusetts said it was "hard to say if we are at the end of hikes."

"The Fed very much wants to keep the door open for additional hikes in December or next year. They did make a few changes to the wording, two of which reflect the assessment that the economy is actually stronger than it was at the last statement," said Hazen, also noting that the Fed changed its reference to job gains from "slowed" to "moderated."

"Both of those are on the positive side," Hazen said.

Earlier the stock market got a boost from falling bond yields after the U.S. Treasury Department said it will slow the pace of increases in its longer-dated debt auctions in the November-January quarter and expects it will need one more additional quarter of increases after this to meet its financing needs.

Earnings has been a mixed bag for stocks even though 79.7% of the 310 S&P 500 companies that had reported at the time of LSEG's latest update, had beat analyst expectations for the quarter while only 16.1% had fallen short of estimates.

Still investors were disappointed by many quarterly updates.

Estee Lauder shares tumbled after the beauty products maker cut its annual profit outlook. And shares in Payroll processor Paycom Software sank after it projected for downbeat fourth-quarter revenue.

Tinder owner Match Group fell after it also forecast fourth-quarter revenue below estimates.