US stocks fell Monday as investors remained concerned that officials in Washington could fail to resolve a looming fiscal crisis. With time running out, investors are increasingly worried about the lack of progress in negotiations over tax increases and government spending cuts set to take effect on January 1. The U.S. dollar gained versus the euro and fell versus the yen. Benchmark light sweet crude oil fell slightly, and gold futures were virtually unchanged. The Dow Jones industrial average fell 51.76, or 0.4 percent, to 13,139.08. The broader Standard & Poorâ€™s 500 index fell 3.49, or 0.2 percent, to 1,426.66. The technology-heavy Nasdaq composite index fell 8.41, or 0.3 percent, to 3,012.60.