Oil prices traded roughly flat in light volumes on Friday, staying near their highest levels since 2015 on pledges from OPEC leader Saudi Arabia and non-OPEC Russia that any exit from crude output cuts would be gradual.

US West Texas Intermediate (WTI) crude future ended Friday’s session 11 cents higher at $58.47.  Brent crude futures, the international benchmark for oil prices, ended the session up 35 cents at $65.25 a barrel, its highest close since June 2015. Both contracts settled one hour early due to the upcoming Christmas holiday. Market liquidity was also drying up on Friday as traders closed positions ahead of the Christmas and New Year breaks. About 280,000 front-month U.S. crude futures changed hands while front-month Brent crude futures saw the lowest trade volumes in about seven months, excluding expiration days. An earlier dip on Friday was due to an outlook for rising supplies that triggered those holding long positions to sell-out ahead of the year-end holidays, traders said.

Also weighing on the market was the expected return of the 450,000 barrels per day (bpd) Forties pipeline system in the North Sea in January. The pipeline, which delivers crude underpinning Brent futures, was shut earlier this month due to a crack. Operator Ineos said on Thursday it expected to complete repairs around Christmas and to gradually restart the system in early January.

Oil prices have recovered in the past year on the back of oil production cuts by OPEC, Russia and other producers, helping reduce the global inventory overhang. Russian Energy Minister Alexander Novak told Reuters OPEC and Russia would exit cuts smoothly, possibly extending curbs in some form to avoid creating any new surplus. “There is a consensus among the (oil) ministers that we should avoid oversupply on the market when exiting the deal,” Novak said, comments that will calm investor worries that Moscow wants a speedy exit. Saudi Energy Minister Khalid al-Falih said it was premature to discuss changes to the pact on supply cuts as market rebalancing was unlikely to happen until the second half of 2018.

The OPEC-led pact to withhold supplies started in January this year. The producer group and its allies agreed to extend the cuts cover all of 2018 from their March expiry. The supply restraint has reduced oil inventories and helped push up Brent by more than 45 percent since June this year. “OPEC’s extension of its production cuts through the end of 2018 is a necessary condition for continued inventory drawdown,” U.S. investment bank Jefferies said.

Jefferies said it has raised its 2018 Brent forecast to $63 a barrel from $57, and its WTI forecast to $59 per barrel from $54, on expectations that the market will remain tight. Novak said some pressure on prices was possible in the first quarter of 2018 when demand traditionally declines and added he saw prices hovering at around $50 to $60 in 2018.

Analysts said crude output in the United States, fast approaching 10 million bpd, would be a drag on prices in the longer term.

“Supply is expected to grow further, paving the way to an oversupplied market, which can again exercise downward pressure on oil prices,” consultancy Rystad Energy said.