Output from the Organization of Petroleum Exporting Countries, OPEC fell by 120,000 barrels a day to 27.05 million a day, with the UAE accounting for most of the drop, according to a Bloomberg survey. 

Modest gains in Libya and Nigeria were offset by similar-sized reductions in Iran and Kuwait.

Led by Saudi Arabia, OPEC and its allies have been withholding crude output for the past few years in an attempt to defend prices against fragile oil demand and plentiful American supplies. Last month, the coalition agreed once again to delay plans for reviving the halted production.

Yet not all members of the alliance have fully delivered the curbs they promised. While OPEC’s own data indicate that Abu Dhabi is abiding by its quota, other estimates including Bloomberg’s survey indicate the UAE is among countries that are overproducing.

The country’s reduction in December may reflect a push for greater discipline. It slashed oil exports to an 18-month low, tanker tracking data compiled by Bloomberg show. State-run oil giant Adnoc is cutting the allocation of crude oil cargoes for some customers in Asia in January and February, according to companies with contracts to receive the shipments.

Nigerian production increased by 40,000 barrels a day to 1.51 million a day, after the country said it had reached a four-year high, according to the survey. Libya extended its recovery from a recent political crisis, adding 40,000 barrels a day to 1.23 million a day, the highest level in more than a decade.