Oil prices edged lower on Friday on doubts about OPEC's planned output cut.
Organization of the Petroleum Exporting Countries experts and counterparts from non-member producers such as Russia started two-day negotiations on Friday on limiting output to curb a global glut that has weighed on markets for two years.
As of late Friday in Vienna, officials had have yet to agree details of a plan to cut oil output and Iran is opposing such a move, OPEC sources said on Friday.
Dow Jones reported the technical meeting was deadlocked as Iran and Iraq disputed the data, with Iran saying OPEC underestimates its production.
Earlier this week, Iraq said it wanted to be exempt from production cuts because it needs oil revenue to carry out a military campaign against Islamic State militants. Baghdad has also quibbled over how OPEC calculates its crude production.