The American economy was more robust in the second quarter than previously reported, according to revised figures that show growth of gross domestic product for the period was 3.3 per cent, ahead of previous estimates of 1.9 per cent.

The revised figures from the Commerce Department compared with a 0.9 per cent increase in the economy in the first quarter.

However, analysts cautioned that much of the GDP growth was driven by the weak dollar, which boosted exports by making America's goods and services cheaper for foreign buyers.

The impact of more than $100 billion (£54.7 billion) worth of tax rebates, made by the US Government to its citizens, also helped to offset the impact of the US housing slump and high energy costs, analysts said.

The US will benefit less in the second half of the year from exports, as the economies of Europe and Japan slow and the dollar continues to gain value.

In addition, as many of the tax rebates have been spent, the economy will not continue to benefit from the fiscal stimulus in the second half.

Lou Crandall, chief economist at Wrightson Icap, said: "The revised GDP figure is certainly not a bad thing, but it is an imprecise estimate of the true health of the economy. It is still the case that GDP could turn negative in the second half."

Brian Fabbri, chief US economist at BNP Paribas, added: "The GDP figure may not say it but this country is still in trouble. Corporate profits have fallen for four consecutive quarters, companies have fired 60,000 workers a month in the past seven months and the outlook for the economy is pretty grim."

Separately, the Labour Department released new figures showing that the number of initial unemployment benefit claims fell by 10,000 to 425,000 in the week ended August 23, marking its third successive weekly decline.

But the jobless figures were in line with expectations and did not reflect a significant change in the underlying economy, analysts said.

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