The Dow Jones Industrial Average tumbled 83.56 points (0.64 percent) to 12,899.39 in opening trade. The tech-rich Nasdaq Composite dropped 22.97 (0.78 percent) to 2,940.78, while the broad-market S&P 500 slid 9.61 (0.70 percent) to 1,356.13. Global oil prices slipped Monday amid profit taking after reaching nine-month highs last week on worries about the impact of heightened Iran tensions on stretched global oil supplies. A weekend G20 meeting of finance chiefs in Mexico ended with the European Union being told it needs to build up a bigger firewall before they would help by boosting the International Monetary Fund's resources. The US equity markets were sinking "following a rebuffed call by Europe for the G20 to boost the IMF's eurozone crisis-fighting capability, while global economic concerns regarding the recent rally in oil prices are weighing on stocks," Charles Schwab analysts said.