U.S. economic growth in the third quarter expanded at an annual rate of 2.1 percent, up from its previous estimate of 1.9 percent, the U.S. Commerce Department reported Wednesday.

According to the second estimate released by the Bureau of Economic Analysis, upward revisions to private inventory investment, non-residential fixed investment, and personal consumption expenditures were partially offset by a downward revision to state and local government spending.

The 2.1 percent growth rate in the third quarter, which is slightly up from the 2 percent in the second quarter, marks a sharp deceleration from the 3.1 percent in the first quarter.

Robert Kaplan, president of the Federal Reserve Bank of Dallas, said in an interview with CNBC on Tuesday that he expected the U.S. economic growth to "be weak" in the fourth quarter of the year as businesses cut inventories due to trade uncertainty.

"One of the reasons the fourth quarter is going to be weak, we believe, is probably a significant inventory adjustment, which might be as much as half a percent or more of GDP (gross domestic product) growth," said the senior Fed official.

According to the latest forecast released by the Federal Reserve Bank of Atlanta last week, U.S. economic growth is expected to fall to an annual rate of 0.4 percent in the fourth quarter.

The Fed has already lowered interest rates three times since July, amid growing risks and uncertainties stemming from trade tensions, weakness in global growth and muted inflation pressures. These policy adjustments put the current federal funds rate target range at 1.5 to 1.75 percent.