Big Board imposes stock trading curbs

NEW YORK (Reuters) - The New York Stock Exchange said on Thursday it instituted downside trading curbs at 9.38 a.m. EDT as U.S. stocks fell sharply in early trading.

A downgrade of Citigroup Inc (C.N), the No. 1 U.S. bank, sparked concerns about the financial sector.

The New York Stock Exchange Composite Index , which is used to determine when to begin trading curbs, was down 212 points, or 2 percent, at 10,099.

The trading curbs require that all program selling of S&P 500 stocks must be on an up-tick.