Qasemi sent the letter after a number of Arabic countries expressed interest in substituting for Iran as oil suppliers to European countries.
The letter urges OPEC members not to aggravate the oil embargo against the Islamic Republic.
"Some OPEC countries should pursue a reasonable policy. Joint cooperation is important between all regional players," the letter said.
According to foreign media outlets, some Arabic countries of OPEC, such as Saudi Arabia, the UAE and Kuwait, expressed readiness to cooperate with Western countries in terms of oil supplies, after the oil embargo was imposed on Iran.
On January 23, EU foreign ministers agreed on Iran's oil embargo banning EU countries from buying Iranian oil in six months.
