WASHINGTON — Federal Reserve Chairman Ben Bernanke said the central bank remains prepared to take additional action if needed to boost the economy, after leaving its policy unchanged Wednesday.

“We remain prepared to do more as needed to make sure that this recovery continues and that inflation stays close to target,” he said at a news conference after a meeting of the Federal Open Market Committee in Washington.

Central bankers upgraded their forecasts for economic growth and unemployment while repeating their view that borrowing costs are likely to remain “exceptionally low” at least through late 2014.

The Federal Open Market Committee “expects economic growth to remain moderate over coming quarters and then to pick up gradually,” it said in a statement at the conclusion of a two-day meeting in Washington. “Despite some signs of improvement, the housing sector remains depressed.”

Policymakers are holding off on additional steps to boost the economy amid signs the more than two-year expansion is gaining strength. That makes a third round of quantitative easing unlikely for now.

Quantitative easing is intended to stimulate an economy through a central bank’s purchase of government bonds or other financial assets, increasing the money supply. In the previous round of easing, the Fed purchased $600 billion in long-term Treasuries.

Despite that, the jobless rate isn’t declining fast enough to satisfy central bankers.

“Strains in global financial markets continue to pose significant downside risks to the economic outlook,” according to Wednesday’s statement. The Fed has cited the risk from strains in global markets in its previous five meetings. In March it said those strains had “eased.”

“If growth is picking up gradually, that may be the final nail in the coffin for ‘QE3’ because most members would only contemplate additional quantitative easing if the economy slowed,” said Chris Rupkey, chief financial economist at Bank of Tokyo-Mitsubishi UFJ in New York, referring to a third round of quantitative easing.

Policymakers upgraded their forecasts for growth and unemployment this year. They now see the jobless rate at between 7.8 percent and 8 percent, compared with January estimates of 8.2 percent to 8.5 percent. The economy is forecast to expand at 2.4 percent to 2.9 percent, compared with 2.2 percent to 2.7 percent.

They raised their forecasts for the inflation rate this year, as measured by the personal consumption expenditures index, to 1.9 percent to 2 percent, from 1.4 percent to 1.8 percent. The forecasts reflect the so-called central tendency, which excludes the three highest and three lowest projections of 17 policymakers.

The central bank said it would continue its swap of $400 billion of short-term debt with long-term debt to lengthen the average maturity of its holdings, a move dubbed Operation Twist. The Fed is scheduled to complete the program at the end of June. The Fed also didn’t alter its policy of reinvesting its portfolio of maturing housing debt into agency mortgage-backed securities.

Inflation “has picked up somewhat, mainly reflecting higher prices of crude oil and gasoline,” the Fed said. Gas prices will affect inflation “only temporarily,” it said.

Oil prices have declined since the Fed’s March meeting, and the national average cost of gasoline has fallen to $3.84 a gallon from a 2012 peak of $3.94 on April 4, according to the American Automobile Association.

Richmond Fed President Jeffrey Lacker dissented for the third meeting in a row. Lacker has said he believes the first increase in interest rates will likely be necessary in 2013.

Fed policymakers met amid renewed concern over Europe’s fiscal crisis. The benchmark Stoxx Europe 600 Index of European countries hit a three-month low on April 23 and has since rallied as companies, including Electrolux AB, posted earnings that beat estimates.

In the United States, consumer spending is starting to power growth as business investment cools. A report Wednesday showed that orders for durable goods fell in March by the most in three years, indicating manufacturing will contribute less to growth this year.

Retail sales rose more than forecast in March as Americans snapped up everything from cars and furniture to clothes and electronics. The 0.8 percent gain was almost three times as large as projected and followed a 1 percent advance in February, Commerce Department figures showed April 16.

A government report Friday may show that gross domestic product rose at a 2.5 percent annual rate, according to the median forecast in a Bloomberg News survey of economists, driven by the biggest increase in household demand in a year.

Corporate earnings and an improving economic outlook are powering stock-market gains. The S&P 500 is up more than 10 percent this year.

Central bankers have already taken unprecedented steps to boost the economy as it battled the longest and deepest recession since the Great Depression and its aftermath.

The Fed lowered its target interest rate to a range of zero to 0.25 percent in December 2008, and it purchased $2.3 trillion of assets in two rounds to push down longer-term borrowing costs.