UPDATE 9-Brent crude slips, demand outlook weighs

* IEA cuts 2011, 2012 oil demand growth forecast

* US crude stocks expected to have fallen last week - poll

* Brent premium to U.S. crude narrows

* Coming up: EIA oil stocks data, 10:30 a.m. EDT Wednesday (Updates with API data and shut pipeline news paragraphs 14-18, 20)

By Robert Gibbons

NEW YORK, Sept 13 (Reuters) - Brent crude prices slipped on Tuesday, dragged down by spread selling and a downward revision to the International Energy Agency's forecast for growth in global oil consumption due to the struggling economy.

Traders extended a deep sell-off in the premium of Brent to U.S. crude futures into a second day, with the spread narrowing more than $2 to under $22 a barrel as U.S. futures pushed above $90 to their highest in five weeks.

Brent traded lower after the IEA revised its forecast for global oil demand down by 160,000 barrels per day (bpd) for 2011 and by 190,000 bpd for 2012, citing financial and economic headwinds. [ID:nL5E7KD10U]

"Brent crude and the U.S. product markets are weaker, on demand concerns reinforced by an (IEA) monthly report that trimmed demand," Tim Evans, energy analyst at Citi Futures Perspective in New York, said in a note.

ICE Brent October crude fell 36 cents to settle at $111.89 a barrel, after briefly turning positive in afternoon trading in New York. The October Brent contract expires on Thursday.

The more heavily traded November Brent contract lost 42 cents to settle at $109.77 a barrel.

"With Libyan production expected to rise, we think Brent traders are increasingly comfortable selling into the forward market, while they are less certain over the balance for nearby October," Evans said.

U.S. October crude rose $2.02 to settle at $90.21 a barrel, highest close since Aug. 3, gaining further support from expectations weekly inventory reports would show a decline in U.S. stockpiles.

U.S. gasoline futures rose slightly and heating oil , benchmark for spot distillates trades, slipped.

Brent's premium to U.S. crude fell to $21.91 a barrel, after its surge to a record above $27 last week. The record peaks in 2011 resulted, in part, from the disruption of Libya's supplies by civil war.

In its report, the IEA raised its forecast for Libyan crude oil production by the end of 2011, which would increase global supplies of light, sweet crude, especially for Libya's primary pre-civil war customers in Europe.

"We still view the $22-25 zone as a sweet spot for the nearby Brent-WTI spread, at least until some cargoes of Libyan supply into Europe are realized," Jim Ritterbusch, president at Ritterbusch & Associates, said in a research note.

Brent and U.S. crude trading volumes both exceeded their 30-day averages.

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U.S. OIL INVENTORIES

U.S. crude and Brent crude were little changed in post-settlement trading after industry group American Petroleum Institute's weekly inventory report showed crude stocks fell 5.1 million barrels last week, more than expected by analysts.

Gasoline stocks had a surprise build of 2.8 million barrels, while distillate stockpiles rose 67,000 barrels, the API said.

Ahead of the API report, a survey of analysts yielded a forecast for crude stocks to have fallen 3.1 million barrels last week on disrupted production and imports due to Tropical Storm Lee. [EIA/S]

Distillate stocks were expected to be up 700,000 barrels and gasoline inventories down 500,000 barrels.

Another potential supply glitch appeared on Tuesday when Chevron said it shut down the Main Pass crude oil system in the Gulf of Mexico off the coast of Louisiana to investigate a potential leak. [ID:nS1E78C1PP] [ID:nS1E78C0U1]

High retail prices cut into U.S. gasoline consumption and made the 2011 summer driving season the worst for gasoline demand since 2009, MasterCard said on Tuesday. [ID:nS1E78C12H]

The U.S. Energy Information Administration's weekly inventory report is due at 10:30 a.m. EDT (1430 GMT) on Wednesday. (Additional reporting by Gene Ramos in New York, Jessica Donati in London and Alejandro Barbarosa in Singapore; Editing by Dale Hudson, Andrea Evans and David Gregorio)