Stocks briefly add losses on energy drag
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 and hopes for cheaper gasoline for consumers during the holiday shopping season.
* A disappointing profit warning from drugmaker Merck -- traditionally thought to be able to withstand tough economic times -- raises concerns that the economic slump is reverberating more broadly and worsening.
Exxon Mobil shares dropped 2.4 percent to $77.03, making the stock the second-top drag on the Dow, behind Chevron , which was off 2.5 percent at $72.84.
(Reporting by Ellis Mnyandu; Editing by Jan Paschal)