The Dow Jones industrial average (INDU) fell 19 points, or 0.1%, according to early tallies. The index had been up by 70 points earlier in the session. The S&P 500 (SPX) and the Nasdaq (COMP) both lost about 1 point.

Speaking in Atlanta, Bernanke acknowledged that economic growth this year has been slower than expected. But he said growth should pick up in the second half of the year if gas prices "moderate" and the supply disruptions stemming from the disaster in Japan fade.

Bernanke twice called the job market "far from normal" and conceded, "the economy is still producing at levels well below its potential."

Despite the challenges facing the economy, Bernanke reiterated that the central bank's $600 billion stimulus will run out later this month.

However, Bernanke left the door open for more accommodative monetary policy, saying interest rates are likely to remain "exceptionally low" for an extended period, and did not dismiss the idea of further easing. He also said that should his inflation predictions be wrong, the Fed "would respond as necessary."