(Dec 21): Angola announced it’s leaving the Organization of the Petroleum Exporting Countries (Opec) following 16 years of membership amid a fractious dispute over oil production quotas.

Luanda had rejected a reduced output limit imposed by the leaders of the cartel to reflect the country’s dwindling production capacity. State-owned Jornal de Angola reported the decision, citing Mineral Resources Minister Diamantino Azevedo.

Angola’s departure will shrink membership of Opec to 12 nations. Led by Saudi Arabia, the group and its allies have been reining in supplies to shore up flagging oil prices. Brent futures slipped 1% on Thursday to trade just below US$79 a barrel.

“It was not a decision made lightly — the time has come,” Azevedo said after a cabinet meeting. “Our role in the organisation was not deemed relevant.”

Luanda’s clash with Opec’s leadership began in the summer, when it was asked to accept a reduced production target for 2024 that recognised its fading abilities. The country’s output has collapsed about 40% over the past eight years to about 1.14 million barrels a day as it fails to invest sufficiently in ageing, deepwater oil fields, Bloomberg data shows.

It was promised a review by external consultants, but this produced an even worse outcome: At its latest meeting last month, Opec imposed a lower quota of 1.1 million barrels a day, below the nation’s current output.

“As a country, when we participate, it is to contribute, expecting results that align with our interests,” Azevedo said. “When this doesn’t occur, we become redundant, and it no longer makes sense for us to remain in the organisation.”

Several other members have quit the group in recent years, for different reasons: Qatar, Indonesia and most recently, Ecuador. Opec, headquartered in Vienna, didn’t immediately comment.