 "Fed holds steady on stimulus, worried by fiscal drag")
Expressing concern about a drag from Washington's belt-tightening, the Fed described the economy as expanding moderately in a statement that largely mirrored its last policy announcement in March. Fed officials cited continued improvement in labor market conditions and did not change their description of inflation, saying it should remain at or below the central bank's 2% target.
But policymakers reiterated that unemployment is still too high and restated their intention to keep buying assets until the outlook for jobs improves substantially.
"Fiscal policy is restraining economic growth," the US central bank's Federal Open Market Committee said in its policy statement at the close of its two-day meeting. "The Committee is prepared to increase or reduce the pace of its purchases to maintain appropriate policy accommodation."
Some economists were surprised that the statement did not contain a clearer acknowledgement of a recent weakening in the economic numbers.
Until recently, analysts had expected the Fed to buy a total of $1 trillion in Treasury and mortgage-backed securities during its ongoing third round of quantitative easing, known as QE3, with expectations the Fed would start to take its foot off the accelerator in the second half of this year.
Now, things are looking a bit more shaky.
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"The talk of tapering has not only been pushed to the back burner but pushed off the stove altogether. It's not something we're likely to see until 2014," said Michael Woolfolk, senior currency strategist at BNY Mellon in New York.
Wall Street stocks finished close to 1% lower after initially paring losses following the Fed statement, and the US dollar weakened in choppy trade.
The president of the Kansas City Fed, Esther George, dissented for a third straight meeting on Wednesday against the Fed's support for growth, citing concerns about financial imbalances and long-term inflation expectations.
Economic growth rebounded in the first quarter after a dismal end to 2012, but the 2.5% annual rate of expansion fell short of economists' estimates, and forecasters are already penciling in a weaker second quarter.
The housing market continues to show signs of strength. However, the industrial sector is not quite as perky, with a report on Wednesday showing national factory activity barely grew in April.
And the job market, the focus of much of the Fed's efforts, remains sickly. US employers added only 88,000 workers to their payrolls in March, while private-sector data on Wednesday suggested continued weakness in hiring.
At the same time, inflation has steadily been coming down. The Fed's preferred measure of core inflation, which excludes more volatile food and energy costs, rose just 1.1% in the year to March. Overall inflation was up just 1%, the smallest gain in 3-1/2 years.
The Fed targets inflation of 2%.
Checking the toolkit
In response to a deep financial crisis and recession, the Fed cut overnight interest rates to effectively zero in late 2008. It has also bought over $2.5 trillion in assets, more than tripling its balance sheet, to keep long-term rates low.
If the economy's fortunes do not improve, the central bank may well look for fresh ways to boost its support to the economy, and increasing the amount of assets it is buying is just one option.
The Fed could announce an intent to hold the bonds it has bought until maturity instead of selling them when the time comes to tighten monetary policy. Fed Chairman Ben Bernanke has already raised this as a possibility.
Policymakers could also set a lower unemployment threshold to signal when the time might be ripe to finally raise rates. Currently, the threshold stands at 6.5%, provided inflation does not threaten to breach 2.5%.
Research suggests such "forward guidance" about the future path of interest rates can have a strong impact on current borrowing costs, and one Fed official -- Narayana Kocherlakota, president of the Minneapolis Federal Reserve Bank -- has already suggested lowering the threshold to give the economy a boost.