WASHINGTON (Reuters) - Strong exports and consumer spending supported by government stimulus cheques pushed the US economy ahead at a solid 3.3 percent annual rate in the second quarter, much stronger than first thought, but growth is expected to flag as those factors fade.

The US Commerce Department yesterday said consumer spending and net exports were more robust than initially estimated and that inventories fell less sharply. A month ago, it had said US Gross Domestic Product had expanded at a 1.9 percent rate in the quarter.

The revised GDP figure was much stronger than the 2.7-percent gain Wall Street analysts had expected.

The report added to evidence the US economy may skirt the downturn many had forecast as a result of a deep decline in housing markets, tight credit and high energy and food prices.

US stocks were up more than one percent at midday on the economy's unexpected vigour and the dollar pared losses against the euro, while Treasury debt prices fell.

"It's clear that the second quarter not only wasn't a recession quarter, it was actually a very robust quarter," said Michael Englund, chief economist for Action Economics in Boulder, Colorado.

GDP had grown at a sluggish 0.9 percent rate in the first quarter after a 0.2 percent contraction in the final three months of 2007. The fourth quarter of last year was the weakest since July-September 2001, when the economy was in recession.

The Federal Reserve has held benchmark interest rates at two percent since April to bolster the struggling economy. Growth in the second quarter at close to the level of long-term trends could make it easier for the Fed to raise interest rates to combat troublesome inflation.

However, many analysts worry that exports and consumer spending, which have buoyed the economy, are likely to taper off in the second half of the year as government-support spending dries up and weakening global growth and a stronger US dollar crimp demand from abroad.

"This number seems to overstate the underlying strength even though exports are obviously strong," said James O'Sullivan, an economist at UBS Securities in Stamford, Connecticut.

Consumer spending, which fuels two-thirds of the US economy, grew at an upwardly revised 1.7 percent rate in the second quarter rather than the 1.5 percent pace first reported.

Meanwhile, exports grew at a 13.2 percent annual rate instead of the 9.2 percent pace initially estimated. In all, a narrowing trade gap contributed more than three percentage points to GDP growth.

Housing, however, continued to be a sore spot. Residential construction fell at an annual 15.7 percent pace, slightly more than the 15.6 percent decline reported earlier.

Meanwhile, inventories dipped at an annualised $49.4 billion in the quarter, rather than the $62.2 billion drop first reported, a possible sign that businesses are less pessimistic than believed.

In a separate report, the Labor Department said the number of US workers filing new claims for jobless benefits fell by 10,000 last week, although it remained at elevated levels indicating a weak labour market.