Oil prices dipped early on Friday, weighed down by lingering doubts over whether OPEC can coordinate a crude production cut big enough to rein in oversupply that has dogged markets for two years.
International Brent crude oil futures LCOc1 were trading at $50.39 per barrel at 0033 GMT, down 8 cents from their last close.
US West Texas Intermediate (WTI) crude was down 5 cents at $49.67 a barrel.
Traders said there were significant doubts that the Organization of the Petroleum Exporting Countries (OPEC) would be able to rally its members and non-OPEC producers, especially Russia, around a significant cut in output.
"With both Iraq and Iran saying they won't be part of the cuts for various reasons, and Russia talking freezes not production cuts, the onus will fall on Saudi Arabia to pull any deal together," said Jeffrey Halley, senior market analyst at brokerage OANDA in Singapore.
"OPEC's Nov. 30 meeting suddenly seems like a long way away with seemingly half of the group wanting exemptions now," he added.