He also warned: "Inflation has obviously surprised to the upside over the past year, and further surprises could be in store".

The Fed this month hiked rates by 75 basis points and is expected to do the same in July, with some observers predicting two more such moves after that.

After a day of swings, Wall Street ended in negative territory, though off big early lows.

Asia fluctuated after a big sell-off Wednesday, with optimism at a premium among investors and analysts saying it is unlikely to improve anytime soon.

Hong Kong, Sydney, Singapore and Wellington were slightly higher but Tokyo, Shanghai, Seoul, Taipei, Manila and Jakarta fell.

"Having listened to Powell's lengthy Senate testimony... it is clear that inflation is the domestic issue at the top of the political agenda," said SPI Asset Management's Stephen Innes.

"Powell consistently bobbed and weaved his way through commenting on anything of fiscal nature but was focused on deploying the tools within the Fed's power to address their dual mandate" of reining in inflation and keeping unemployment in check.

"So we should still position for more rate hike fallout to occur."

Powell's comments came as other top economists added to the recession talk, with former New York Fed President Bill Dudley saying it was "inevitable within the next 12 to 18 months".

And Deutsche Bank CEO Christian Sewing said there was a 50 per cent chance of a contraction next year.

Elon Musk, JP Morgan boss Jamie Dimon and Nouriel Roubini are among several others to have made similar forecasts.

"We are still in an era where uncertainty is elevated and is expected to remain so for quite a while," said JoAnne Feeney, of Advisors Capital Management, on Bloomberg Television.

"It's risky right now in terms of the forward outlook for the global economy. Recession risk has clearly risen."

The prospect of a retreat in the global economy continued to drag oil prices down as traders fret over demand, with both main contracts down more than three percent, having tumbled on Wednesday.

Brent and WTI have dropped around 15 percent over the past week, even with sanctions on Russian crude exports and China's gradual reopening from lockdowns.

Adding to the selling was data Wednesday indicating a jump in US stockpiles.

"A slowdown in global growth is a risk to oil demand, which could help ease some of the tightness in the market," Warren Patterson, at ING Groep, said.

"Already, we have seen demand estimates revised lower."