Stocks suffered their worst day in nearly a month on Monday as concern about the stalemate in U.S. budget talks and growing debt problems in the euro zone prompted investors to hedge against further losses.

The Dow Jones industrial average <.DJI> dropped 151.44 points, or 1.20 percent, to end unofficially at 12,505.76. The Standard & Poor's 500 Index <.SPX> lost 24.31 points, or 1.81 percent, to finish unofficially at 1,319.49. The Nasdaq Composite Index <.IXIC> fell 57.19 points, or 2.00 percent, to close unofficially at 2,802.62.

(Reporting by Chuck Mikolajczak; Editing by Jan Paschal)