U.S. Federal Reserve Chair Jerome Powell warned Wednesday of the threat of a prolonged recession resulting from the viral outbreak and urged the U.S. Congress and the White House to act further to prevent long-lasting economic damage.

The Fed and Congress have taken far-reaching steps to counter what is likely to be a severe downturn resulting from the widespread shutdown of the U.S. economy. But Powell cautioned that widespread bankruptcies among small businesses and extended unemployment for many people remain a serious risk.

"We ought to do what we can to avoid these outcomes," Powell said.

Additional rescue aid from government spending or tax policies, though costly, would be "worth it if it helps avoid long-term economic damage and leaves us with a stronger recovery," he said.

U.S. President Donald Trump on Tuesday again pushed the Fed to adopt negative interest rates, a hot topic in financial markets since last week when U.S. money market instruments started to price in a chance of negative rates.

The chairman said the Fed would "continue to use our tools to their fullest" until the viral outbreak subsides, but he gave no hint of what the Fed's next steps might be.

However, he said he is not considering using negative interest rates.

"I know there are fans of the policy, but for now it's not something that we're considering," the chief said Wednesday.

After Powell's speech, Trump tweeted that "When the so-called 'rich guys' speak negatively about the market, you must always remember that some are betting big against it, and make a lot of money if it goes down."

(With input from AP and Reuters)