Oil prices inched lower on Monday as investors gave up some of their bullish bets on another price hike and the likelihood that major producers will agree to limit output appeared to fade.
Iran has announced that it will continue to ramp up production and exports until it reaches pre-sanction levels.
Saudi Arabia, which brokered the February meeting that resulted in the yet to be implemented output freeze agreement, last week reiterated that it would not proceed with the deal unless Iran was on board, while Russia just hit its highest oil output in three decades.
All these developments have cast doubt on the feasibility of the freeze agreement.
Representatives from 15 oil-producing countries are set to meet this month in Doha to discuss how they can best address the oversupply and the falling prices.
Brent crude futures shed 28 cents to trade at $38.39 a barrel by 0845 GMT, while U.S. crude futures gave up 38 cents at $36.41 a barrel.
Oil has fallen more than 65% since the middle of 2014, after U.S. shale oil output and supply rose significantly, which was then matched by OPEC and Russia to defend market share.
Prices rallied in March on renewed hopes of a freeze output, but recently pronouncements by major players are making investors wary.