WASHINGTON (Reuters) - The U.S. economy grew faster than initially thought in the second quarter amid strong consumer spending, while corporate profits rebounded, which should help to sustain the expansion.

Gross domestic product increased at a 3.0% annualized rate last quarter, the Commerce Department's Bureau of Economic Analysis said in its second estimate of second-quarter GDP on Thursday. That was an upward revision from the 2.8% rate reported last month.

The economy grew at a 1.4% pace in the first quarter. Economists polled by Reuters had forecast GDP would be unrevised at a 2.8% pace.

Consumer spending, which accounts for more than two-thirds of the economy, increased at an upwardly revised 2.9% rate. It was previously reported to have grown at a 2.3% pace. That offset downgrades in business investment, exports and private inventory investment.

Spending is being supported in part by wage gains, but momentum is slowing as the labor market shifts into lower gear. Personal income increased by $233.6 billion in the second quarter, a downward revision of $4.0 billion from the previous estimate.

Corporate profits including inventory valuation and capital consumption adjustments increased $57.6 billion after declining by $47.1 billion in the first quarter.

Profits of domestic financial firms increased $46.4 billion, while those of non financial institutions rose $29.2 billion, more than offsetting a $18.0 billion decline in profits from the rest of the world.

When measured from the income side, the economy grew at a 1.3% rate last quarter. Gross domestic income (GDI) increased at a 1.3% pace in the January-March quarter.

In principle, GDP and GDI should be equal, but in practice they differ as they are estimated using different and largely independent source data.

The average of GDP and GDI, also referred to as gross domestic output and considered a better measure of economic activity, increased at a 2.1% rate last quarter after advancing at a 1.4% pace in the first quarter.