Though part of the increase in output came from the reversal of temporary factors that had restrained growth, the expansion was a welcome relief for an economy that looked on the brink of recession just weeks ago.
US gross domestic product expanded at a 2.5 per cent annual rate in the third quarter, the Commerce Department said in its first estimate.
That was a jump from the 1.3 per cent pace in the April-June quarter and matched economists' expectations.
"It is a relief, but there is still more work to be done to continue a sustainable recovery," said Sean Incremona an economist at 4CAST in New York.
U.S. Treasuries prices pared losses on the report, while the dollar fell against the euro and the yen.
U.S. stocks looked set for a 2 percent jump at the open on Thursday after European leaders agreed on a bailout fund for the region.
Consumers and businesses appeared to have set aside their fears about the recovery in the third quarter.
Consumer spending was the strongest since the fourth quarter of 2010, while business investment spending was the fastest in more than a year.
Even businesses had not anticipated the fairly strong demand and were slow to restock warehouses.
The peppier spending and a slower pace of inventory accumulation by businesses will lay a base for a solid fourth quarter, but a slowdown in Europe and the exhaustion of pent-up U.S. demand could leave a weak spot early in 2012.
And the recovery's pace is still too weak to lower a jobless rate that has been stuck above nine per cent for five straight months.
A separate report from the Labour Department showed new claims for state unemployment benefits fell 2,000 last week to a seasonally adjusted 402,000, pointing to a gradual improvement in the labour market.