Iran has urged fellow OPEC members to refrain from any unilateral measures to increase oil production.
Tehran's letter to OPEC's president on Sunday follows reports that Saudi Arabia had agreed with U.S. President Donald Trump to raise its oil production to two million barrels to offset a decline in supply from Iran.
Iran reacted to that tweet moments later saying Trump's request was no different to asking the Kingdom to leave the oil cartel.
In Sunday's letter, Iranian Oil Minister Bijan Zanganeh didn't mention Saudi Arabia by name, but urged members to adhere to the bloc's agreement last month to pump an additional one million barrels of crude oil a day in July.
He said breaching that agreement would undermine the unity and independence of OPEC.
After Trump pulled the U.S. out of the Iran nuclear deal, Tehran is trying to counter U.S. sanctions that would restrict its exports and eat into its market share.
Oil prices have also been rising amid political instability in Venezuela and Libya.