U.S. stocks fell Monday, June 25 as investors lowered their expectations for a key summit of European Union leaders later this week.

"It's Europe again," said Peter Boockvar, chief market strategist with Miller Taback & Co. "The market is expecting nothing new to come out of the summit."

The Dow Jones industrial average tumbled 170 points, or 1.3%, in midday trading. The S&P 500 slid 24 points, or 1.8%, and the Nasdaq sank 59 points, or 2%.

Bank of America, Microsoft and Caterpillar were the worst performers on the Dow. Wal-Mart managed small gains as investors gravitated toward shares of companies that are considered defensive, such as consumer staples.

While financial crisis in Europe, investors are also worried about the global economy following a string of weak reports on manufacturing, among other things, CNNMoney reported.