Reuters - 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 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 concrete parameters for a deal to restrict output.

Reporting by OPEC Newsroom; Editing by Dale Hudson