According to reports, U. S. markets turned sharply lower Tuesday after credit-rating agency Standard & Poor's downgraded Greek debt to junk status.

It was also reported that the move makes it questionable whether Greece can use its debt as collateral as it attempts to negotiate loans with the European Central Bank and the International Monetary Fund, which it was counting on to help dig itself out of a debt crisis.

On the positive side, the S&P Case-Shiller home-price indexes showed U. S. home prices in February rose in both the 10- and 20-city indexes for the first time since December 2006.

The Dow Jones industrial average, by close, was down 1.9 percent, 213.04 points, to 10,991.99. The Standard & Poor's 500 index lost 2.34 percent, 28.34 points, to 1,183.71. The Nasdaq composite index lost 2.04 percent, 51.48 points, to 2,471.47.

492 stocks advanced and 2,593 declined on a volume of 7.4 billion shares traded on the New York Stock Exchange.

There was a rise of 30/32 in the benchmark 10-year Treasury note to yield 3.695 percent.

From Monday's $1.3368, the euro fell to $1.3174. The dollar, against the yen, fell to 93.21 yen from Monday's 94.01 yen. (With Inputs from Agencies)