NEW YORK (Reuters) - Merck & Co Inc (MRK.N: Quote, Profile, Research), whose earnings have been hurt by patent expirations and declining sales of its Vytorin cholesterol fighter, said on Monday it will eliminate another 1,200 members of its U.S. sales force as part of a restructuring begun in late 2005.

Merck spokeswoman Amy Rose said the job cuts will follow the elimination of about 400 members of the drugmaker's U.S. sales force since early 2007.

"That represents a 20 percent reduction of our sales force," Rose said, referring to the combined cuts of 1,600 positions since early last year.

(Reporting by Ransdell Pierson; editing by Jeffrey Benkoe, Richard Chang)