Federal Reserve chairman Ben Bernanke says the economic recovery in the United States has softened more than expected.
The Commerce Department announced on Friday that the US economy grew at an annual rate of 1.6% - significantly lower than the government's first estimate of 2.4%.
The figure confirms fears that growth is slowing sharply and that the US might be facing another recession.
Economists say the US economy needs to grow at about 3% just to stop the unemployment rate of 9.5% from rising.
Mr Bernanke says the Federal Reserve will do whatever is necessary if it needs to bolster the economy.
In a review of the US economy at the Fed's annual Jackson Hole symposium in Wyoming, Mr Bernanke expressed particular surprise at the rise in the savings rate of US consumers and a sharp rise in the US trade deficit.
He also noted that business investment in structures - such as commercial real estate - had failed to rebound.
In order for the recovery to be sustained, he said, consumer spending and business investment needed to pick up more quickly.
The US economy emerged from recession with a 1.6% growth rate in the third quarter of 2009.
Housing sales down
Earlier this week, it was reported that sales of existing homes in the United States plunged 27.2% in July compared with June to their lowest level in more than 10 years.
According to the National Association of Realtors, home sales completed in the month stood at an annualised rate of 3.83 million.
The NAR said the main reason for the drop was the end of tax credits designed to boost sales.