[WASHINGTON] The US economy grew faster than initially thought in the third quarter, notching its best performance in two years, amid solid consumer spending and a jump in soybean exports.

Gross domestic product increased at a 3.5 per cent annual rate instead of the previously reported 3.2 per cent pace, the Commerce Department said in its third GDP estimate on Thursday.

Growth was the strongest since the third quarter of 2014 and followed the second quarter's anemic 1.4 per cent pace.

Output was also lifted by upward revisions to business investment in structures and intellectual property products, underscoring the economy's solid fundamentals, which contributed to the Federal Reserve raising interest rates last week.

Economists polled by Reuters had expected that third-quarter GDP growth would be revised up to a 3.3 per cent rate.

When measured from the income side, the economy grew at a 4.8 per cent pace, instead of the previously reported 5.2 per cent clip. That was the fastest pace of increase in gross domestic income since the second quarter of 2014 and followed a 0.7 per cent rate of increase in the second quarter.

Consumer spending, which accounts for more than two-thirds of US economic activity, increased at a three per cent rate in the third quarter and not the 2.8 per cent pace reported last month. That was still a slowdown from the second quarter's robust 4.3 per cent pace.

Spending on nonresidential structures, which include oil and gas wells, increased at a 12 per cent rate, the fastest pace since the first quarter of 2014. Nonresidential outlays were previously reported to have increased at a 10.1 per cent pace.

The export growth estimate was revised a touch lower to a 10 per cent rate from the previously reported 10.1 per cent pace. It was the fastest pace since the fourth quarter of 2013. The spike in exports largely reflected a surge in soybean exports after a poor soy harvest in Argentina and Brazil.

Businesses accumulated inventories at a US$7.1 billion rate in the last quarter, rather than the US$7.6 billion pace reported last month.

REUTERS