NEW YORK (Reuters) - Stocks briefly added to losses on Thursday, sending benchmark indexes close to session lows as a continued drop in oil prices pushed down shares of energy companies, including Exxon Mobil .
Highlights:
* Indexes fall more than 1 percent; U.S. front-month crude drops $2.25, or nearly 5 percent, to $44.53 a barrel.
* The energy sector drag offsets optimism from solid sales at Wal-Mart Stores Inc
* A disappointing profit warning from drugmaker Merck
Exxon Mobil shares dropped 2.4 percent to $77.03, making the stock the second-top drag on the Dow, behind Chevron
(Reporting by Ellis Mnyandu; Editing by Jan Paschal)