Oct. 24 (Bloomberg) -- Trading in futures on the Standard & Poor's 500 Index, the Dow Jones Industrial Average and the Nasdaq 100 Index was limited until U.S. markets open to stop the contracts from extending losses of more than 6 percent today.

The S&P 500 futures will not trade below 855.20, the so- called limit down level this quarter, until U.S. regular trading begins at 9:30 a.m. New York time, said Jeremy Hughes, a London- based spokesman for the Chicago Mercantile Exchange.

Dow Average futures won't trade below the 8,224 level, he said, while the Nasdaq 100 futures won't fall below 1,168.50. The ``limit down'' suspension allows the contracts to trade above those levels, he said.

Stocks tumbled around the world today and U.S. index futures sank on deepening concern the global economic slump will crimp corporate earnings. The S&P 500 futures slid 6.6 percent while contracts on the Dow average slipped 6.3 percent.

``When the selling becomes so heavy there are very few places to hide,'' said Richard Robinson, who helps oversee $1.8 billion at Jersey-based Ashburton Ltd. ``It is an extremely risk-averse market.''

The ``limit down'' restriction thresholds are calculated on a quarterly basis. The New York Stock Exchange plans to open for U.S. trading today, NYSE's New York-based spokesman Richard Adamonis said.

To contact the reporter on this story: Sarah Jones in London at sjones35@bloomberg.net; Alexis Xydias in London at axydias@bloomberg.net.

Last Updated: October 24, 2008 07:43 EDT