The US economy expanded more than previously estimated in the second quarter on stronger consumer spending and construction, the second upward revision in a row. 

The Commerce Department said the country's gross domestic product rose at a 3.9% annual pace in the three months from April to June, up from 3.7% reported last month. 

The rise, which beat expectations in a Reuters poll for the third reading of Q2 economic growth to be unchanged at 3.7%, was driven by growth in consumer spending, mainly on services like healthcare and transport. 

Consumer spending, which accounts for more than two thirds of US economic activity, was revised up to a 3.6% growth pace from the 3.1% rate reported in August.

Spending was helped by cheap petrol prices and relatively higher house prices boosting household wealth. 

Revised construction spending data helped to push up the headline figure, with non-residential fixed investment expanding 4.1% in the quarter. 

The revisions to second-quarter growth also reflected a smaller accumulation of inventories than earlier estimated, with inventories contributing just 0.02 percentage point to growth rather than adding 0.22 percentage point.

After-tax corporate profits were also stronger in the second quarter than previously thought. 

Profits after tax with inventory valuation and capital consumption adjustments showed a 2.6% rebound from a slump in late 2014 and early 2015, instead of the 1.3% increase reported last month. 

The data supports the case that the US economy may be gaining enough strength to withstand an increase in benchmark interest rates from record low levels.

 The US Federal Reserve last week held off from raising rates, but Fed Chair Janet Yellen kept the door open to an increase this year in a speech last night, as long as inflation remains stable and growth is strong enough to boost employment.