In her first public speech since becoming Fed chair two months ago, Janet Yellen cited the struggles of three American workers to back up the central bank's policies of low interest rates and continued bond buying.
She said considerable slack still exists in the job market, a sign that further monetary stimulus can still be effective.
"I think this extraordinary commitment is still needed and will be for some time, and I believe that view is widely shared by my fellow policy-makers at the Fed."
The Fed has held interest rates near zero for more than five years now.
The central bank says it will keep rates there for a considerable time even after it ends its bond-buying program, which is on course to be wound down later this year.
Yellen said the U.S. economy remains well short of the Fed's goals of maximum sustainable employment.
"This commitment is strong, and I believe the Fed's policies will continue to help sustain progress in the job market. but the scars from the Great Recession remain, and reaching our goals will take time."
U.S. stocks rose on Monday, with the Standard & Poor's 500 ending March with moderate gains.
Yellen's remarks calmed investors, many of whom had grown anxious the Fed might raise short-term rates by mid-2015.
Ji Myung-kil, Arirang News.