Oil prices edged lower on Friday and were set for the biggest weekly losses in six weeks over doubts about whether OPEC and non-OPEC oil producers will be able to agree on an output cut big enough to curb a global glut that has weighed on markets for two years.
Experts from the Organization of the Petroleum Exporting Countries and counterparts from other oil-producing nations such as Russia started two-day negotiations on Friday over an output-capping agreement expected to be presented at the end of next month.
Disagreements remain over which members should be exempt from a curb to reduce output to a range of 32.5-33 million barrels per day (bpd).
Brent crude futures were down 16 cents at $50.31 a barrel at 0823 GMT (4:23 a.m. ET). The contract was set to close the week more than 2 percent lower in its steepest weekly loss since mid-September.
U.S. West Texas Intermediate (WTI) crude was down 27 cents at $49.45 a barrel, also on track for its biggest weekly loss in six weeks.
"Doubts linger about OPEC's ability or willingness to implement any production cuts," said analysts at Cenkos Natural Resources.
"The market has been wary of reading too much into the rhetoric ahead of the next meeting scheduled for the end of November."
French oil major Total said on Friday it expected crude prices to remain volatile and continued to reduce costs.
The French company said it loses around 2 billion euros in cashflow for every $10 downward move in oil prices.
Weak prices have also hit Italian oil firm ENI, which reported a worse-than-expected quarterly loss on Friday.
(Additional reporting by Henning Gloystein in Singapore; editing by Jason Neely)