NEW YORK, Jan. 10 (Xinhua) -- U.S. stocks ended mixed on Monday after European debt problems once again plagued the market.

European stocks fell after European media reported that France and Germany were pressing Portugal to accept outside aid to prevent Europe's financial crisis from spreading. Portugal had denied the offer.

Italy, Spain and Portugal are each scheduled to sell bonds this week. Investors are now worried that the debt crisis could spread and Spain might be dragged in to the mire.

Meanwhile, Alcoa Inc. will release its results after the Monday market closes.

The Dow Jones industrial average dropped 37.31 points, or 0.32 percent, to 11,637.45. The Standard & Poor' s 500 index declined 1.75 points, or 0.14 percent, to 1,269.75, and the Nasdaq rose 4.63 points, or 0.17 percent, to 2,707.80.