JACKSON HOLE, Wyoming — Chairman Ben Bernanke is proposing no new steps by the Federal Reserve to boost the U.S. economy while hinting that Congress may need to act to stimulate hiring and growth.

Bernanke said today that while record-low interest rates will promote growth over time, the weak economy requires further help in the short run. He is speaking at an annual economic conference in Jackson Hole, Wyoming.

His speech follows news that the economy grew at an annual rate of just 1 percent this spring and 0.7 percent for the first six months of the year. Only slightly healthier expansion is foreseen for the second half.

Bernanke said he’s optimistic that the job market and the economy will return to full health in the long run.

Stocks fell lower after the speech was released. The Dow had been down about 78 points, about 0.7 percent, shortly before 10 a.m. The loss quickly extended to 145 points.

In his speech, Bernanke left open the possibility that the Fed will take further steps to strengthen the economy. He said its September meeting will be held over two days instead of just one.

The Fed chairman said long-term deficit reduction is necessary. But he emphasized that future economic health could be jeopardized if hiring and growth are not strengthened now.

“Fiscal policymakers should not … disregard the fragility of the current economic recovery,” he said.

Bernanke also was critical of Congress’ handling of this summer’s battle over raising the debt ceiling. He said it disrupted the economy, and another episode like that could have long-term negative consequences.

Bernanke’s speech comes at a critical moment for the economy. Some economists worry that another recession might be near.

A big reason is that consumer spending has slowed. Home prices are depressed. Workers’ pay is barely rising. Household debt loads remain high.

All that, compounded by Europe’s debt crisis, has spooked the stock markets and unnerved consumers. Congress is focused on shrinking deficits and seems unlikely to back any new spending to try to energize the economy.

That’s why many have looked with anticipation to the Fed to do more. The central bank has already kept short-term interest rates near zero for 2 1/2 years. And earlier this month, it said it would keep them there through mid-2013.