The Dow Jones Industrial Average dropped 22.06 points (0.18 percent) to 12,192.32 around 1455 GMT, after closing in positive territory Tuesday for the first time in three sessions amid easing oil prices.

The broad-market S&P 500 index retreated 4.31 points (0.33 percent) to 1,317.51, while the tech-rich Nasdaq Composite shed 14.55 points (0.53 percent) at 2,751.22.

"The US equity markets are giving back some of yesterday's strong advance as oil prices are gaining some ground and traders are grappling with lingering Middle East unrest and resurfacing euro-area debt concerns," Charles Schwab analysts said in a client note.

There were no major US economic releases on the calendar to lure interest away from the intensifying unrest in the oil-producing Arab world.

Crude oil prices rose in New York and London as forces loyal to Libyan leader Moamer Kadhafi continued to attack rebels seeking his ouster.

A series of massive explosions erupted into fireballs near an oil facility outside the rebel-held town of Ras Lanuf.

On Wall Street, it was a weak start to the second-year anniversary of the bear market lows struck on March 9, 2009, when the Dow finished at its lowest level since 1997, at 6,547.05 points. Since then the blue-chip index has rebounded 87 percent.

Wednesday's pullback was broad. On the 30-stock Dow, only a few components were trading higher: pharmaceutical giant Merck, 0.5 percent; pharma and health care products company Johnson & Johnson, 0.2 percent; and the world's largest retailer Wal-Mart, 0.7 percent.

Dow heavyweight IBM, though, helped limit the slump, rising two percent to $165.55 after an analysts conference.

Government bailed-out insurer American International Group rose 0.6 percent to $37.54. AIG repaid $6.9 billion to the US Treasury Tuesday thanks to the sale of its equity stake in US rival MetLife.

Electronics manufacturer Texas Instruments plunged 2.9 percent to $34.83 after lowering forecasts for the 2011 first quarter.

On Tuesday, the major indexes had been lifted by easing oil prices, pushing the Dow up 1.03 percent.

The bond market firmed. The yield on the 10-year Treasury fell to 3.52 percent from 3.54 percent late Tuesday, while that on the 30-year bond dipped to 4.64 percent from 4.66 percent.

Bond prices and yields move in opposite directions.