OPEC ministers are set to decide whether to cut production across the 14-member oil cartel, a move that could send oil prices rising even further.
The November 30 meeting in Vienna was being overshadowed by regional geopolitics, as Saudi Arabia and Iran jostled for economic, and regional, advantage.
Iran has been rushing to rebuild its oil export capacity now that a landmark nuclear deal has lifted Western sanctions and allowed for more investment within Iran.
Tehran is now looking to regain market share within OPEC. It's also looking to push the Saudis to give up gains it says were made while Iran was under sanctions.
But Saudi Arabia remains OPEC's, and one of the world's, largest producers.
Global crude prices fell about 4 percent ahead of the meeting as it appeared uncertain that a cut might be agreed upon, according to Reuters.
Russia and other major non-OPEC producers had also signaled readiness to cooperate with production cuts in September, but their committment has since waned.
The cartel's dominance over world oil prices in the 1970s and 1980s has ebbed in recent years, particularly as the United States has unlocked previously untapped shale oil and gas deposits.
That's turned the U.S. into one of the world largest exporters.