By Timothy Puko, Sarah McFarlane and Biman Mukherji 

Oil prices are posting some of their largest one-day gains of the year as investors show optimism about output cuts from the world's biggest exporters and the possibility they'll be extended at next week's OPEC meeting.

A surge above $50 a barrel for U.S. crude is its first since late April. Gains on Friday would be the ninth in 11 sessions, a sharp turnaround since falling to a five-month low early this month.

The market has been buoyed in that span by long-awaited declines in U.S. crude stockpiles. They have been some of the first since the Organization of the Petroleum Exporting Countries spearheaded global production cuts to start the year, a move that many had expected to cause a steady rally.

U.S. crude for June delivery recently gained $1.09, or 2.2%, to $50.44 a barrel on the New York Mercantile Exchange. Brent, the global benchmark, gained $1.15, or 2.2%, to $53.66 a barrel on ICE Futures Europe.

There are few new headlines pushing further gains Friday, analysts and brokers said. But recent trends have continued.

Many spot markets are stronger, suggesting the OPEC cuts are having an effect and making supply a little harder to come by, said Scott Shelton, broker at ICAP PLC. And the recent shift in momentum gets accelerated by systematic trading programs, which now appear to be buying again after a long period of selling, he added.

"The markets are really starting to see the effects of the cuts. People are really starting to struggle for barrels," Mr. Shelton added, though he cautioned that there are signs of rising production too. "There are a lot of fits and starts."

The meeting's topic next Thursday will include whether OPEC and other major producers should extend beyond mid-2017 the six-month deal on production cuts of 1.8 million barrels a day and for how long, and whether there should be more severe cuts.

"The expectation is now that we at least get a deal that is a nine-month extension and the same depth of cuts. And for OPEC to impress the market, they might need to do more," said Richard Mallinson, analyst at consultancy Energy Aspects. For instance, the group may consider a bigger cut, he said.

Bank of America Merrill Lynch pointed out that OPEC is struggling to bring down global stocks but that the cartel's own strong production in the fourth quarter, ahead of the cuts, has made it harder to achieve its goal.

Earlier this week, energy officials from Saudi Arabia and Russia signaled they back a nine-month extension. That helped kick-start a rise in prices, with U.S. and Brent crude on track for weekly gains of nearly 6%.

To some, the price rebound was to be expected after April's slide. That drop "was a case of sentiment over substance," said BMI Research. It sees more price gains to come over the next several months, but they "are more likely to be incremental rather than exponential."

Gasoline futures recently gained 2.9% to $1.6532 a gallon and diesel futures rose 2.8% to $1.5891 a gallon.

Write to Timothy Puko at tim.puko@wsj.com, Sarah McFarlane at sarah.mcfarlane@wsj.com and Biman Mukherji at biman.mukherji@wsj.com

(END) Dow Jones Newswires

May 19, 2017 13:10 ET (17:10 GMT)