Wall St. opens lower on concern over Russia, nixed deals

NEW YORK (Reuters) - U.S. stocks opened lower Wednesday on worries of an escalation of the conflict in the Russia-Ukraine border and after two large merger and acquisition deals fell through.

NATO said Wednesday Russia has amassed around 20,000 combat-ready troops on Ukraine's eastern border and could use the pretext of a humanitarian or peace-keeping mission to invade.

The Dow Jones industrial average fell 55.55 points or 0.34 percent, to 16,373.92, the S&P 500 lost 8.76 points or 0.46 percent, to 1,911.45 and the Nasdaq Composite dropped 25.49 points or 0.59 percent, to 4,327.35.

(Reporting by Rodrigo Campos; Editing by Bernadette Baum)