Iran on Tuesday undercut hopes of an agreement to limit petroleum output next month, saying it doesn’t expect that its production will have risen to the levels the country has said it needs to justify cooperation with its rivals.

The spotlight has been on Iran in recent weeks after the Organization of the Petroleum Exporting Countries, a 14-nation cartel that counts Iran as a member, said it would hold discussions in late September about whether action was needed to lift oil prices. While global production has fallen back...