WASHINGTON, Dec. 21 (Xinhua) -- U.S. economy expanded at an annual rate of 3.2 percent in the third quarter of the year, slightly lower than 3.3 percent previously estimated, according to the final revision of U.S. gross domestic product (GDP) by the Commerce Department.

"With this third estimate for the third quarter, personal consumption expenditures increased less than previously estimated, but the general picture of economic growth remains the same," the department said Thursday in a report.

Personal consumption expenditures, which accounts for about two-thirds of the U.S. economy, increased at an annual rate of 2.2 percent in the third quarter, slightly lower than 2.3 percent previously estimated.

The slight revision didn't change the fact that U.S. economy had expanded above three percent in back-to-back quarters for the first time since 2014. The economy expanded at a rate of 3.1 percent in the second quarter.

The economic growth is likely to gain further momentum next year as the 1.5-trillion-U.S. dollar tax cuts package approved by Congress this week is set to take effect in 2018.

But the Federal Reserve last week estimated that the U.S. economy would grow at 2.5 percent both in 2017 and 2018 even with the tax changes, still below the Trump administration's ambitious growth objective of over three percent.

"My colleagues and I are in line with the general expectation among most economists that the type of tax changes that are likely to be enacted would tend to provide some modest lift to GDP growth in the coming years," Fed Chair Janet Yellen said last week.