Producers are struggling with low oil prices and an oversupplied market but have been loath to cede market share by cutting output.
Instead, OPEC members Saudi Arabia, Qatar and Venezuela reached a preliminary agreement with Russia in February to freeze production at January levels.
They will seek backing for that deal from other producers at Sunday's meeting in Doha, Qatar.
Iran's oil minister had not been scheduled to attend, but Tehran was due to send Iran OPEC Governor Hossein Kazempour Ardebilli, oil ministry news agency Shana reported on Friday.
Sources told Reuters that Iran had been informed that only those countries willing to agree to freeze their output level should attend.
Iran has said it supports the freeze but would not join it until it raises its output and market share to their pre-sanctions levels.
Sanctions imposed by the United States and other world powers were lifted in January in return for Tehran agreeing to long-term curbs on its nuclear programme.
A rise in Iran's oil output will undermine efforts to rebalance the market in 2016, a Reuters poll of oil analysts showed this week.
Its production has already surpassed 3.5 million barrels per day (bpd) and exports are set to reach 2 million bpd next month, Iran's deputy oil minister was quoted as saying by state news agency IRNA on Saturday. - Reuters
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