OPEC members Ecuador and Libya expressed concern Wednesday that the cartel was pumping too much oil, but shied away from calling for lower output on the eve of a ministerial meeting.
The crucial production meeting is held against the backdrop of sliding prices, which have shed more than 25 percent since March on the back of weak demand, abundant supplies and global economic turmoil.
"I think it is oversupplied," Ecuador's Natural Resources Minister Wilson Pastor told reporters.
"There is 1.6 million barrels a day too much production," above the 30 million-barrels-per-day OPEC ceiling.
He said he would ask that the Organization of Petroleum Exporting Countries (OPEC), whose 12 member nations pump one third of the world's crude supplies, maintain the ceiling at 30 mbpd on Thursday.
Libya also voiced concern about oversupply which it estimated to be even higher at 1.8 mbpd.
OPEC hawks Venezuela and Iran want OPEC to trim output to boost prices but the cartel's kingpin Saudi Arabia is concerned that this could hinder economic recovery across the globe.
OPEC will also use its meeting on Thursday to discuss the election of a new secretary-general, with Libyan Abdullah El-Badri retiring at the end of the year.
Iran and Saudi Arabia are vying for the position, along with Ecuador and Iraq.
Pastor, speaking ahead of an energy seminar at Vienna's Hofburg Palace on Wednesday, said: "It would be an honour for Ecuador and South America but we will see."
OPEC is headquartered in the Austrian capital.