NEW YORK - April 27, 2010 - U.S. stocks followed European markets sharply lower Tuesday after Standard & Poor's downgraded the debt of Portugal and Greece. The rating agency's move intensified investors' fears that Europe's debt problems are spreading.

The Dow Jones industrial average fell more than 150 points. All the major market indexes were down more than 1%.

Investors have been on edge for months about Greece's fiscal crisis even as they've sent stocks higher on signs of an improving U.S. economy. They have also been worried that Portugal could be the next weak European economy to require help. That has undermined confidence in Europe's shared currency, the euro.