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.