(REUTERS) -- U.S. stocks fell 1 percent at the open on Tuesday on renewed concerns that Greece and private bondholders may not meet a looming deadline to complete a debt swap and as caution grew over the global economic outlook.

The Dow Jones industrial average lost 129.41 points, or 1.00 percent, to 12,833.40. The S&P 500 Index dropped 14.05 points, or 1.03 percent, to 1,350.28. The Nasdaq Composite fell 33.09 points, or 1.12 percent, to 2,917.39.

(Editing by Jeffrey Benkoe)