Oil prices remained little changed on Friday, lingering below two-year highs as the continuing outage of a North Sea pipeline and OPEC-led production cuts supported prices, while climbing U.S. output kept a lid on gains.U.S West Texas Intermediate (WTI) crude futures ended Friday’s session 26 cents higher at $57.30 a barrel. Brent Crude futures, the international benchmark for oil prices, were at $63.26 a barrel, down 5 cents from their previous close at 1:57 p.m. ET (1857 GMT).

“There’s a fight in the market,” said Gene McGillian, senior analyst at Tradition Energy in Stamford, Connecticut. Speculators have staked out long positions, betting that production cuts will continue to remove oversupply from the market, he said. Analysts at Barclays said product inventory levels in industrialized nations were 2 percent below the five-year average at the start of December, compared with 10 percent above the five-year average at the start of 2017, with the drawdown driven by a combination of outages and strong demand growth.

On the other side, U.S. production is seen rising in response to higher prices. Goldman Sachs said market conditions allowed major oil companies, or Big Oil, to enter “a positive earnings-revision cycle.” It added: “This should allow Big Oil to re-employ capital at double-digit returns.” “Exactly how that is going to play out is going to be the determinant of how our prices move in the first half of the year,” Tradition’s McGillian said.

U.S. energy companies this week cut oil rigs for the first time in six weeks in spite of prices rising close to their highest in over two years and drillers starting to boost spending plans for next year. The oil rig count fell by four to 747 in the week to Dec. 15, General Electric Co’s Baker Hughes energy services firm said in its closely followed report on Friday.

The ongoing outage of the Forties pipeline, which carries North Sea oil to Britain, was the main price support early in the session, traders said. The outage’s main physical impact is the North Sea region, but it has global relevance as the crude is used to underpin the Brent price benchmark. Operator INEOS declared force majeure on Forties, the first such declaration in decades. Force majeure is a legal designation that suspends a firm’s contractual obligations due to situations beyond its control.

Beyond the North Sea supply disruption, traders and analysts said markets were generally supported by efforts led by the Organization of the Petroleum Exporting Countries and Russia to withhold production to prop up prices. Undermining OPEC’s efforts to tighten the market is U.S. oil production, which has soared by 16 percent since mid-2016 to 9.78 million barrels per day (bpd), close to levels of top producers Russia and Saudi Arabia.

Rising U.S. supply, driven largely by shale drilling, will likely move oil markets into a supply surplus in the first half of 2018, the International Energy Agency (IEA) said on Thursday.