US stocks tumbled Monday, joining global equity markets in retreat on the looming threat of a Greek debt default.

At the closing bell, the Dow Jones Industrial Average stood at 17,600.06, down 346.62 points (1.93 percent). The broad-based S&P 500 sank 43.74 (2.08 percent) to 2,057.75, while the tech-rich Nasdaq Composite Index dropped 104.33 (2.33 percent) to 4,958.97.