* Saudi Arabia has cut supply by 8 pct -OPEC president
* Russia offers OPEC "concrete support"
* US stocks down on economic gloom (Recasts, updates prices, market activity; changes dateline, previously LONDON)
NEW YORK, Dec 15 (Reuters) - Oil prices eased on Monday as deepening economic worries countered expectations that OPEC would agree to its biggest supply cut ever when the group meets in Algeria this week.
U.S. crude <CLc1> fell 42 cents to $45.86 a barrel by 12:30 p.m. EST (1730 GMT), off a session high of $50.05. London Brent crude <LCOc1> fell 39 cents to trade at $46.02 a barrel.
Dealers said they were eyeing stock market losses amid worries about the world economy, even as OPEC and top non-OPEC producer Russia said they likely would agree to slash output.
"We're in a tug of war," said Jim Ritterbusch, president at Ritterbusch and Associates in Galena, Illinois.
Economic turmoil has slammed energy demand growth and contributed to a slide in oil prices of more than $100 per barrel since the peak over $147 in July.
Analysts at Goldman Sachs have said prices could drop as low as $30 a barrel. OPEC ministers, who meet on Wednesday, are calling for the largest output cuts ever to combat rising inventories and sagging demand. [
]Russia is sending its highest ranking delegation ever to the meeting in Algeria -- including heads of its five top oil companies -- in another sign the world's top non-OPEC producer is willing to clinch a deal to protect oil prices. [
]Oil dropped to a four-year low of $40.50 a barrel on Dec. 5 as the slumping global economy depresses demand in large consumer nations such as the United States.
Saudi Arabia, OPEC's most influential member, identified $75 a barrel as a "fair" price for crude in November, while Iran's oil minister said over the weekend that the "real price" of oil should be more than $100 a barrel. [
]After slashing a combined two million barrels daily, 7.3 percent of its output at two previous meetings, OPEC was expected to chop production by at least another 5 percent to help draw down global inventories.
"We think should OPEC go for anything less than 2 million barrels a day, participants would be inclined to use this as a selling opportunity," said Edward Meir of MF Global in a research note.
"The cartel is simply too far behind the curve to consider anything less than that."
OPEC President Chakib Khelil said the amount of crude oil stored on tankers around the world by oil producers and international companies may have swelled to the equivalent of one full day's worth of global output as the economy slows. [
]"Everybody is supporting a cut -- I don't have any doubt about it. The Saudis have already taken a decision ahead of the meeting, as you know, they have reduced their supply to the market by 8 percent, which has had an affect on the market," Khelil told reporters. [
]In China, the world's second biggest energy consumer, implied oil demand shrank by about 3.5 percent in November from the year before, the first decline in nearly three years, Reuters calculations showed. [
] (Reporting by Matthew Robinson and Robert Gibbons in New York; Jane Merriman in London; Maryelle Demongeot in Singapore and Osamu Tsukimori in Tokyo; Editing by David Gregorio)