OPEC is once again driving the oil market.

Oil prices pared gains on Friday, Sept. 21, following a report that the Organization of Petroleum Exporting Countries may increase output.

OPEC and non-member nations, including Russia, will meet in Algeria this weekend to review compliance with existing production cuts. The group is reportedly discussing the possibility of increasing production by 500,000 barrels per day to blunt the falling supply from Iran due to U.S. sanctions, Reuters reported, citing a source familiar with the talks.

Global benchmark Brent crude futures for November delivery held relatively flat at $78.69 as of about 5:00 p.m. New York time, while West Texas Intermediate crude, the U.S. benchmark, rose 0.6% to $70.71 a barrel.

Exxon (XOM - Get Report) shares rose 0.4% to $$85.17, while Chevron (CVX - Get Report) gained 1.4% to $121.13. Schlumberger (SLB - Get Report) , the oil services giant, slipped by 0.7% to $61.13, and its rival Halliburton  (HAL - Get Report) gained 0.8% to $40.71, all in trading today on the New York Stock Exchange.

The potential for an increase in production follows commentary from the International Energy Agency earlier this month that "if Venezuelan and Iranian exports do continue to fall, markets could tighten and oil prices could rise without offsetting production increases from elsewhere." The Paris-based organization said Brent crude oil prices could hit $80 a barrel if the recent rate of production decline continues.

On Thursday, President Donald Trump criticized the organization, tweeting that "the OPEC monopoly must get prices down now!"

We protect the countries of the Middle East, they would not be safe for very long without us, and yet they continue to push for higher and higher oil prices! We will remember. The OPEC monopoly must get prices down now!

— Donald J. Trump (@realDonaldTrump) September 20, 2018

A potential increase in OPEC production means "there will be less demand for U.S. crude in coming months," and that should also pull Brent prices down, said Sandy Fielden, director of commodity and energy research at Morningstar. "I think the Brent price strength is more to do with short-term supply issues."

Meanwhile, U.S. oil producers have slowed their drilling and production, which have supported WTI prices. Active oil rigs fell by one to 866, according to Baker Hughes (BHGE - Get Report) . Domestic crude oil inventories also decreased by 2.1 million barrels from the previous week, the Energy Information Administration reported on Wednesday.

"At 394.1 million barrels, U.S. crude oil inventories are about 3% below the five year average for this time of year," the EIA said.