Is it enough?

The Fed's decision comes amid financial market turmoil as worries about the global economy escalate after an embarrassing downgrade of U.S. debt. In addition, fears remain that European efforts to put a safety net under heavily indebted Italy and Spain may not suffice to avert wider credit market disruptions.

In an attempt to tamp down market volatility, finance ministers and central bankers of the Group of Seven major world economies held a telephone conference on Sunday and then issued a statement saying they were ready to act to ensure global stability.

Officials had been pinning hopes for an acceleration of U.S. growth in the second half of the year on a healing of supply chain disruptions from Japan's natural disasters, a calming of Europe's debt problems as governments committed to more sustainable fiscal paths and steady gains in business and consumer confidence in the United States.

But those expectations, along with the Fed's forecast for a growth rate of between 2.7 percent and 2.9 percent in 2011, have appeared increasingly over-optimistic in recent weeks.