New York's main contract, light sweet crude for delivery in November, dived $1.04 to $84.77 a barrel.

Brent North Sea crude for November delivery shed 74 cents to $109.99.

"Oil this morning is edging down a sum," said Victor Shum, senior principal of Purvin and Gertz energy consultants in Singapore.

"OPEC (Organisation of the Petroleum Exporting Countries) adjusted its demand outlook for 2012 downward. Also, the news about Slovakia yesterday did not rectify enhancement of the euro financial rescue fund," he told AFP.

"Both news items injected some pessimism into the oil market outlook."

OPEC on Tuesday lowered its estimated world demand for a third month running to 87.81 million barrels per day, down from a September forecast of 87.99 million bpd.

The reduction was due to uncertainty in the global economy and weaker oil demand from China and India, the oil cartel said.

Meanwhile, Slovak lawmakers' rejection of a revamp of the European Financial Stability Facility (EFSF) bailout dealt a further blow to market sentiments amid the European debt crisis.

The blow effectively blocks the expansion of the eurozone's 440-billion-euro ($600 billion) bailout fund even as European Central Bank chief Jean Claude Trichet that the world faced systemic dangers.

The country's leaders have said they would try to pass the EFSF revamp in a repeated vote with support from the opposition, but no date has been fixed for that vote yet.