Crude prices fell on Monday in the first trading session after OPEC-members failed to agree on output targets to reduce a bulging glut that has resulted in oil prices falling by more than 60 percent since June 2014.

The Organization of the Petroleum Exporting Countries failed to agree on an oil production ceiling on Friday at a meeting that ended in acrimony after Iran said it would not consider any production curbs until it restores output scaled back for years under Western sanctions.

This compounded an oil glut that sees production exceed demand between 0.5-2 million barrels per day and that has resulted in a more than 60 percent price drop since 2014.

U.S. crude was trading at $39.58 a barrel at 0038 GMT, down 39 cents. Internationally traded Brent futures were down 16 cents at $42.84 per barrel. This left both benchmarks near 2015 lows and not far off levels seen during the peak of the global financial crisis of 2008/2009.

Analysts said that OPEC would likely maintain its production around current levels of 31.5 million barrel per day and that a decision on how to handle new volumes expected to come to the market once western sanctions against Iran are dropped would be delayed until the group's next meeting in June 2016.

"Past communiques have at least included statements to adhere... or maintain output in line with the production target (of 30 million barrels per day). This one glaringly did not," Barclays bank said.

Not only did OPEC decide to keep its output target high, but analysts said that it would likely continue to exceed its quota as individual members offer discounts to customers in defense of market share.

Barclays said that OPEC faced an "impossible trinity of achieving higher market share, higher prices and higher demand through a nominal target which members continue to breach."

As a result of ongoing oversupply, analysts said that prices would fall further, with Goldman Sachs seeing a possibility of $20 per barrel.

"The effective removal of the OPEC quota leaves the market in a more vulnerable position. Prices are likely to weaken this week as the market turns its attention back on U.S. supply," ANZ bank said, referring to near record U.S. crude inventories of almost 490 million barrels.

"The formal production target was not even discussed, essentially signalling to the market that members would continue production at individual requirements. With Iran exports likely to start increasing next year, this increases the likelihood of further weakness in crude oil markets," it added.