The producer group decided at a December 22 meeting in Angola to keep its output policy unchanged, but faces a battle to crack down on those in its ranks who are failing to comply with quotas if it wants to drain fuel stocks.
"The level of Opec members' compliance with the quota restrictions was about 66 percent in 2009, which was a success," ISNA news agency quoted Mohammad Ali Khatibi, Iran's Opec governor, as saying. He gave no further details.
A Reuters survey last month said Opec's oil supply rose in December to a 2009 high, further eroding compliance with agreed output targets. The survey implied Opec had made 58 percent of promised supply cutbacks, down from 60 percent in November and a peak of 81 percent in March and April.
Iran's output was 410,000 bpd above target in December, the most in absolute terms of any member. For a year, Opec has kept its output ceiling at 24.84 million bpd after making a record supply cut in late 2008 as recession eroded demand and sent prices sliding.
Compliance with the accord has waned as prices recovered during 2009. According to Opec, the 11 members subject to output limits pumped 26.63 million bpd in November, 1.79 million bpd more than the target.