Federal Reserve Chairman Ben Bernanke told lawmakers Wednesday the Fed is ready to act if the economy gets weaker. He warned them that allowing the nation to default on its debt would send "shock waves through the entire financial system."

Underscoring how fragile the economy remains two years after the Great Recession, Bernanke laid out three new steps the Fed could take, including a fresh round of government bond purchases designed to stimulate economic growth.

"We have to keep all the options on the table. We don't know where the economy is going to go," Bernanke told the House Financial Services Committee.

The Fed chairman stopped short of promising anything, but Wall Street appeared comforted that the central bank was poised to act. The Dow Jones industrial average was up more than 150 points during his testimony to Congress, and closed up 45.

But some of the early stock gains were lost after Richard Fisher, president of the Federal Reserve Bank of Dallas, said in a speech that the Fed had already "pressed the limits of monetary policy."

The nation was creating about 200,000 jobs a month this spring. But hiring slowed almost to a standstill in June, with 18,000 new jobs. It takes about 125,000 a month just to keep up with population growth.

While Bernanke made his twice-yearly appearance before Congress, lawmakers and the White House were trying to salvage talks on how to reduce the federal deficit and whether to raise the limit on what the government can borrow.