Excluding Iraq, the 12 members bound by output agreements pumped an average 29.85 million b/d in March, 80,000 b/d lower than February's 29.93 million b/d, the survey showed.
Despite the dip in output from the OPEC-12, the March total was 177,000 b/d higher than their collective 29.673 million b/d crude production target.
Decreases in Iraqi, Venezuelan and Nigerian production totaling 160,000 b/d were partly offset by 50,000 b/d of increases from Iran, Ecuador and Qatar.
OPEC ministers met in February and March and decided on both occasions that despite crude prices in excess of $100 per barrel, there was no shortage of crude oil on world markets. The next formal OPEC ministerial meeting is scheduled for early September.
The group's president, Algerian oil minister Chakib Khelil, said earlier Tuesday that although it was possible OPEC could meet on the sidelines of the upcoming International Energy Forum in Rome, the probability of a meeting was "very low."
Khelil, who reiterated the view that current prices were not being driven by any shortage of crude supply, said he believed high oil prices were "here to stay."
US Energy Secretary Samuel Bodman said Monday he remained "optimistic" that OPEC would raise production despite the organization having ignored requests from the Bush administration to boost output at its February and March meetings.