By Jonathan Cheng

U.S. stocks tumbled Wednesday after the Federal Reserve said it would extend its "Operation Twist" program to support the economy.

The Dow Jones Industrial Average lost 68 points, or 0.5%, to 12766, after trading lower by about 30 points prior to the announcement. The Standard & Poor's 500 index lost nine points, or 0.7%, to 1349, and the Nasdaq Composite declined 15 points, or 0.5%, to 2917.

The Dow initially dropped as many as 90 points before bouncing back modestly in the following minutes. The euro also dropped as the dollar moved higher. Gold was largely unchanged after the announcement, off about 1.3% on the day.

The Fed's monetary policy statement will be followed by a press conference at 2 p.m.

Write to Jonathan Cheng at Jonathan.Cheng@wsj.com