Citi shares are down more than 30 percent as investors worry about their holdings in the company being diluted by the move.
Word that the economy, as measured by the gross domestic product, fell at a 6.2 percent annual pace in fourth quarter is adding to investors' worries.
The Standard & Poor's 500 index has breached its Nov. 21 trading low of 741.02, which many investors had hoped would mark the bottom of the market's fall from October 2007.
The Dow Jones industrial average is down 117 at 7,065, while the S&P 500 index is down 16 at 737. The Nasdaq composite index is down 16 at 1,375.