Fed vows to use 'full range' of tools to help economy

"We will continue to use our tools to ensure that the recovery, when it comes, will be as robust as possible."

For now, he said, monetary policy is calibrated appropriately, but added that could change. "It may well be the case that the economy will need more support from all of us if the recovery is to be a robust one," Powell said.

In a matter of weeks the U.S. economy has gone from historically low unemployment to seeing more than 26 million people file for unemployment benefits and the sharpest plunge in activity since the Great Recession, as authorities across the country shut down large swaths of industry and commerce to slow the spread of the virus.

Gross domestic product declined at a 4.8% annualized rate in the first quarter, ending the longest expansion in U.S. history, the Commerce Department reported earlier on Wednesday.

Powell said he expects second-quarter GDP to shrink by double digits and for there to be significant increases in unemployment. It also will "take some time" for consumers to start spending again once the economy begins to reopen, he said.