* U.S. inventories down by 6.5 mln barrels, more than expected
* Kuwait oil minister says OPEC/non-OPEC compliance at 122 pct
* North Sea Forties pipeline shut due to crack
* Goldman Sachs says OPEC/non-OPEC may roll back cuts in 2H 2018 (Updates throughout, adds EIA data, adds quotes, changes byline, dateline, previous LONDON)
NEW YORK, Dec 20 (Reuters) - Crude prices firmed modestly on Wednesday, supported by a larger-than-expected drop in U.S. inventories and the continued outage of the North Sea Forties pipeline system.
U.S. crude stocks fell by 6.5 million barrels, more than expected, in the week to Dec. 15, while gasoline stocks rose 1.2 million barrels, less than anticipated, the Energy Information Administration said on Wednesday.
West Texas Intermediate crude futures gained 20 cents to $57.79 a barrel as of 11:03 a.m. EST (1603 GMT), while Brent crude was up 39 cents to $64.20 a barrel.
Crude stocks, excluding the U.S. Strategic Petroleum Reserve, are at 436.5 million barrels, lowest since October 2015.
"That bodes well to support crude oil prices into 2018 as I expect inventories to continue to decline with robust crude exports being supplied by increases in production," said Andrew Lipow, president of Lipow Oil Associates in Houston.
Inventories have been steadily declining in the United States due to strong export demand and efforts by major oil producers to restrict supply.
OPEC and 10 other producers led by Russia last month extended an agreement to cut oil production by 1.8 million bpd until the end of next year.
The alliance is targeting the elimination of an oil glut to bring inventories in the developed world back to the five-year moving average.
On Wednesday, Kuwait's oil minister Bakhit al-Rashidi said compliance among both OPEC and non-OPEC members currently stands at 122 percent, the highest since the deal was implemented in January, helping bring stocks down.
Traders said rising U.S. crude production <C-OUT-T-EIA>, which has soared by 16 percent since mid-2016 to 9.8 million bpd, was capping prices. The all-time U.S. production record of more than 10 million bpd was set in the early 1970s and is based on monthly EIA figures.
Most analysts expect U.S. output to break through 10 million bpd soon, which would be a new record and take it to levels on a par with top exporter Saudi Arabia and close to top producer Russia, which pumps around 11 million bpd.
Goldman Sachs said on Wednesday that it expects global oil inventories will have rebalanced by mid-2018, "leading to a gradual exit from the cuts and increases in OPEC and Russia production through second half 2018."
The bank added that a ramp-up in OPEC production and rising non-OPEC output "will leave risks skewed to lower prices" in the second half of next year.
Prices have been supported by the continuing outage of Britain's Forties pipeline in the North Sea, which delivers crude underpinning Brent futures.
Operator Ineos said repairs were under way on Wednesday after a crack was found that closed the pipeline on Dec. 11. Repairs are expected to take two to four weeks. (Additional reporting by Scott DiSavino in New York, Ahmad Ghaddar in London and Henning Gloystein in Singapore, Editing by Phil Berlowitz)