By David Sheppard
LONDON (Reuters) - Brent crude slipped near $81 a barrel on Wednesday, close to a four-year low as a mounting oil glut created by the U.S. shale boom continued to outweigh concerns about supplies from Libya.
With oil prices having fallen 30 percent since June, OPEC delegates are starting to suggest the producer group could informally cut output by around 500,000 barrels per day (bpd) when it meets in Vienna on Nov. 27.
But delegates within the Organization of the Petroleum Exporting Countries warned an agreement will not be easy, and many oil traders and analysts doubt members will take a decisive stance.
"The consensus view is OPEC won't take any action, or if it does, not big enough or sufficiently definitive to have too much impact on prices," said Ric Spooner, chief market analyst at Sydney's CMC Markets.
Brent for December delivery fell 62 cents to $81.05 by 0900 GMT. It dropped 67 cents on Tuesday after first touching $80.46, its lowest since September 2010.
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U.S. crude was down 66 cents at $77.28 a barrel.
Oversupply, doubts over whether OPEC will cut production and a strong dollar were weighing on prices, said Ben Le Brun, market analyst at Sydney's OptionsExpress.
"I would like to think there is a floor (for Brent) at around $80 a barrel ... but I still see more to play out on the downside," he said.
The market is still assessing whether an OPEC cut of 500,000 bpd would make oil prices more vulnerable to the impact of potential supply disruptions caused by geopolitical risks in Libya and other oil producers, Spooner said.
Exports remained blocked at Libya's 120,000-bpd Hariga port by protesters involved in a wage dispute although talks to resolve the issue were under way, an oil official said on Tuesday. The El Sharara oilfield was also still closed.
"We see few factors in the short term that could stem the decline in prices besides a massive and prolonged outage of Libyan crude, or OPEC intervention," analysts at JBC Energy said in a note, adding they believe OPEC may cut output by 1 million bpd.
U.S. oil inventory data due on Wednesday and Thursday could show a build in crude stocks of 800,000 barrels in the week ended Nov. 7, according to a Reuters poll of analysts.
The weekly fuel stocks data from the American Petroleum Institute and U.S. Energy Information Administration has been delayed by one day due to a federal holiday.
(Additional reporting by Keith Wallis in Singapore; Editing by Dale Hudson)