The Federal Reserve pledged Tuesday to hold interest rates near zero for two more years to counter an economy facing increased risks of stalling.

The US Federal Reserve building in Washington.

But it offered no successor to the $600 billion "QE2" stimulus program that wound up in June, though it said it was reviewing the tools it has on hand to boost a slowing economy.

Meeting as worries grew of a new US recession, the Fed\'s policy board admitted growth so far this year had been "considerably slower" than expected.

It maintained its key interest rate at the ultra-low level of 0-0.25 percent -- in place since December 2008 -- and vowed to keep "exceptionally low" rates "at least through mid-2013."

The Federal Open Market Committee (FOMC) said after a one-day meeting Tuesday that it now expects growth at a "somewhat slower pace" over the coming quarters than it had estimated in June.

And "downside risks to the economic outlook have increased," it added, in a post-meeting statement.

The signal of a concrete period for the low rate was a shift from earlier FOMC statements, which suggested only that the rate would be held for "an extended period" and reflected worries that the low rates could spark a burst of inflation.

The FOMC statement made clear the central bank is no longer concerned about inflation, predicting that it "will settle" over the coming quarters.

But the three inflation hawks on the FOMC objected to setting a timespan for the ultra-low-rate policy, favoring instead the previous formulation that forecast rates at that level for an "extended period."

Meeting for the first time since its QE2, or "quantitative easing" asset purchase program ended in June, the Fed is seen as having few options to overcome stagnating growth and the growing pessimism that sent stock markets on their deepest plunge since the crisis of 2008.

But after the economy grew at around a one percent pace in the first half, US officials have sought to fend off suggestions of a "double-dip" recession, two years after the 19-month "Great Recession" ended in June 2009.

Analysts said before the FOMC meeting that a move to set a timeframe on interest rates could signal that the Fed will continue to stimulate the economy.

But the specific commitment on rates was not seen as uniformly positive.

"After numerous rumors about the Fed\'s reaction to the current economic activity slowdown, the Fed resorted to one of the easiest in implementation monetary policy tools -- communication," Inna Mufteeva of Natixis said in a client note.

"Yet, the explicit promise to keep the Fed Funds low until mid-2013 limits significantly the future flexibility of the FOMC (the apparent reason of three hawkish dissents) and represents quite a hard-line commitment for the Fed."

The Fed meanwhile gave no hint that it was considering a successor to QE2, only that the meeting "discussed the range of policy tools available" to promote growth.

QE2, which ran from November to June, pumped $600 billion into the economy through purchases of Treasury bonds.

That money remains in the system, and the Fed did say it has no plans to reel it in.

"This is an exceptionally dovish Fed statement that downplays the inflation risks and significantly downgrades the Fed\'s assessment of economic growth," said analysts at RDQ Economics.

US stock markets, hoping to sustain a rebound from Monday\'s 5 percent-plus plunge, were higher after the news.

But the dollar dropped, losing 5.3 percent on the Swiss franc, 1.3 percent on the Japanese yen and 1.0 percent on the euro.

"There is nothing here to restore confidence in the dollar. Monetary policy is not holding back economic growth, but maintaining the current stance of policy for the next two years (at least) is likely to foster inflation pressures," said RDQ Economics.