The New York Stock Exchange and NYSE Amex Cash Markets invoked Rule 48 on Monday, as fears of a credit rating downgrade of French banks and the lack of a solution to Greece's debt problem heightened concerns about the euro zone's debt crisis.

Rule 48 is invoked to speed up and smooth trading at the market open when exceptionally high volatility is expected.

S&P 500 futures fell 16.7 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures slumped 160 points, and Nasdaq 100 futures lost 30.75 points.

(Reporting by Chuck Mikolajczak; Editing by Padraic Cassidy)