 "Opec")
Iran appears to be the main obstacle for an Opec oil output deal on Friday as the group's leader Saudi Arabia has yet to agree to exemptions for sanctions-hit Tehran, two Opec sources said.
The Organization of the Petroleum Exporting Countries resumes discussions on Friday in Vienna before heading into a meeting with non-Opec oil producers led by Russia.
On Thursday, Opec failed to agree on concrete parameters for a deal to restrict output.
