WASHINGTON – The Federal Reserve sketched a bleaker outlook Wednesday for the economy, which it thinks will grow much more slowly and face higher unemployment than it had estimated in June.

The central bank now predicts the economy will grow no more than 1.7 percent for 2011. For 2012, it foresees growth of about 2.7 percent. Both numbers are roughly a full percentage point lower than its June forecast.

The Fed sees unemployment averaging 8.6 percent by the end of next year. In June, it had predicted unemployment would drop next year to as low as 7.8 percent. The rate is now 9.1 percent.

The Fed’s gloomier outlook is similar to many private economists’ forecasts. Bank of America Merrill Lynch, for example, expects only 1.8 percent economic growth this year and 2.1 percent in 2012.

Those growth rates are far too low to drive down unemployment.

Speaking at a news conference, Fed Chairman Ben Bernanke acknowledged that the pace of growth will likely remain “frustratingly slow.” If conditions worsen, Bernanke said the Fed would consider buying more mortgage-backed securities to try to further cut loan rates and help the depressed home market. He declined to specify what would trigger such a move.

“We remain prepared to take action as appropriate to make sure the recovery continues,” Bernanke said.

Even so, the Fed said Wednesday that the economy had improved since nearly stalling in the spring. As a result, it’s putting off any new actions so it can gauge the impact of steps it’s already taken.

Fed policymakers made the announcement after a two-day meeting.

In a statement, the officials said consumers have stepped up spending. Still, they said the economy continues to face significant risks, including the debt crisis and risk of recession in Europe.

Speaking at his third news conference of the year, Bernanke cited Europe’s debt crisis as a particular concern. He said the crisis could threaten confidence and hold back growth.

The Fed left open the possibility of taking further steps later to try to boost the sluggish economy. But it gave no hint as to what those moves might be.

“They’re noting the better growth numbers but remain pretty cautious,” said Michael Feroli, a former Fed economist now with JPMorgan Chase & Co.

The vote on the Fed’s policy statement was 9-1. Charles Evans, the president of the Chicago Federal Reserve Bank, dissented. The statement said Evans wanted to take stronger action to try to boost the economy.