• The S&P 500 tumbled to the brink of a bear market on Monday as U.S. stocks extended their steep sell-off in a pre-holiday shortened session, with investors rattled by the U.S. Treasury secretary’s convening of a crisis group and by other political developments.

All three major indexes ended down more than 2 percent the day before the Christmas holiday. The S&P 500 finished about 19.8 percent below its Sept. 20 closing high, just shy of the 20 percent threshold commonly used to define a bear market.

The Dow Jones Industrial Average .DJI fell 653.17 points, or 2.91 percent, to 21,792.2, the S&P 500 .SPX lost 65.52 points, or 2.71 percent, to 2,351.1 and the Nasdaq Composite .IXIC dropped 140.08 points, or 2.21 percent, to 6,192.92.