U.S. stocks opened 1 percent lower and were on track to post their worst weekly losses in nearly a year on Friday after data showed meager growth in the economy while a setback in Washington over a debt deal kept investors nervous.

The U.S. economy grew less than expected in the second quarter, at a 1.3 percent annual rate, as consumer spending barely rose amid higher gasoline prices.

The Dow Jones industrial average <.DJI> was down 121.24 points, or 0.99 percent, at 12,118.87. The Standard & Poor's 500 Index <.SPX> fell 13.58 points, or 1.04 percent, at 1,287.09. The Nasdaq Composite Index <.IXIC> slid 28.57 points, or 1.03 percent, at 2,737.68.

(Reporting by Ryan Vlastelica)