U.S. stocks slumped on Friday as investors worried the economy's recovery might not be sustainable and financials sank as an accounting expert projected a $10 billion write-down for Citigroup .

* The S&P 500 and Nasdaq were down for the month, putting an end to seven straight months of gains. The Dow was flat for the month, but it was the worst one-day percentage loss for the index since July.

* The Dow Jones industrial average <.DJI> fell 249.85 points, or 2.51 percent, to 9,712.73. The Standard & Poor's 500 Index <.SPX> slid 29.92 points, or 2.81 percent, to 1,036.19. The Nasdaq Composite Index <.IXIC> lost 52.44 points, or 2.50 percent, to 2,045.11.

(Reporting by Leah Schnurr; Editing by Kenneth Barry)