* Prices supported by OPEC/Russia led production cuts
* But expected end to Forties pipeline closure caps gains
* U.S. output approaching 10 mln bpd undermines cuts
SINGAPORE, Dec 26 (Reuters) - Oil prices were stable on Tuesday, with Brent crude lingering near 2015 highs on the back of an outlook for healthy demand amid ongoing production cuts led by OPEC and Russia.
U.S. West Texas Intermediate (WTI) crude futures were at $58.50 a barrel at 0141 GMT, up 3 cents from their last settlement.
Brent crude futures, the international benchmark for oil prices, were at $65.25 a barrel, unchanged from their last close, but near the $65.83 per barrel briefly on Dec. 12 - the highest since June 2015.
Brent has risen by 47 percent since mid-2017. The Organization of the Petroleum Exporting Countries (OPEC), the Middle East-dominated producer club, and Russia - the world's single biggest oil producer - have been withholding output in order to tighten the market and prop up prices.
The agreement to cut started last January and is set to cover all of 2018.
Jabar al-Luaibi, oil minister of OPEC-member Iraq, said on Monday there would be a balance between supply and demand by the first quarter of 2018, leading to a boost in oil prices.
"During the first quarter of next year there will be more balance between supply and demand, which will reflect positively on improving global oil prices," he said.
The production cuts come amid healthy global demand, which many analysts expect to hit 100 million barrels per day (bpd) for the first time at some point next year or in 2019.
Keeping a lid on prices for the moment is the expected return of the Forties pipeline system in the North Sea, which can supply up to 450,000 bpd of crude underpinning Brent futures.
The pipeline shut down earlier in December due to a crack, but operator Ineos said the system was being tested following repairs and full flows should return in early January.
In the longer term, efforts by OPEC and Russia efforts to prop up prices could also be undermined by U.S. production <C-OUT-T-EIA>, which has soared by more than 16 percent since mid-2016, fast approaching 10 million bpd.
Only OPEC king-pin Saudi Arabia and Russia produce more, but the United States is fast catching up, largely thanks to shale drillers.
The U.S. rig count <RIG-OL-USA-BHI>, an early indicator of future output, held at 747 in the week to Dec. 22, according to the latest weekly report by Baker Hughes. That's still much higher than a year ago, when only 523 rigs were active, and most analysts expect U.S. output to rise past 10 million bpd within weeks.
(Reporting by Henning Gloystein; Editing by Kenneth Maxwell)