Wall Street enters bear market, oil falls on Greece

US stocks opened more than 1.0% lower on Tuesday, entering a bear market, and US crude oil prices fell to a 2011 low as investors worried about the economic implications of an increasingly likely Greek default.

The S&P 500 index, a broad measure of the US stock market, fell more than 20% from its 2011 high. For many investors, crossing that threshold is a sign that stock losses may be sustained for a longer period of time.

Greece appeared more likely to default on its debt after euro zone finance ministers postponed a vital aid payment to Athens until mid-November.

The impact of a possible default on the global economy and particularly on the banking sector worried markets after the EU ministers said they were reviewing the size of private sector involvement in a second bailout package for Greece.

"The economy is in a protracted slowdown, and until there's a resolution with Greece, that situation will continue to linger over the market," said Robert Pavlik, chief market strategist at Banyan Partners LLC in New York. "This could turn into a self-fulfilling prophecy of recession."

The Dow Jones industrial average fell 237.49 points, or 2.23%, at 10,417.81, while the Standard & Poor's 500 Index lost 22.99 points, or 2.09%, to 1,076.24. The Nasdaq Composite Index was down 32.59 points, or 1.40%, at 2,303.24.

World stocks hit a 15-month low, with the MSCI All-Country World index falling nearly 3.0%.

US crude oil prices dropped to as low as USD 74.95 a barrel, its lowest since Sept, 2010. They last traded 2.5% lower at USD 75.65.

The euro was up 0.29% at USD 1.3207, however, after hitting a near nine-month low against the dollar earlier in the session.

Prices of US Treasuries turned lower after US Federal Reserve Chairman Ben Bernanke said the bank is ready to take further action to promote a stronger economic recovery.

Longer-dated Treasuries lead the losses, with 30-year bonds falling 11/32 in price for a yield of 2.7381%.