The most closely watched stock market index in the United States, the Dow Jones Industrial Average, advanced above the milestone 13,000 mark on Tuesday.

It was the first time the index of 30 key American stocks had touched the 13,000 level since May 2008. After reaching that mark in late-morning trading in New York, the index slid just under it, but later topped it again.

Analysts said investors' confidence in the market was buoyed by the European approval of a new bailout for debt-ridden Greece and higher U.S. corporate earnings.

The U.S. economy has struggled to regain its footing after the recession that officially ended in mid-2009, the worst American downturn in seven decades. But even as numerous corporations have moved slowly to boost hiring of more workers, they have amassed millions of dollars in cash reserves from rising profits.

The Dow index includes some of the best known U.S. corporations, including the American Express credit card company, the Boeing aircraft manufacturer, the McDonald's fast food chain and the Walt Disney entertainment empire.