Iranian Deputy Foreign Minister for Arab Affairs Hossein Amir Abdollahian said that although reforms were needed in Syria, those issues are internal affairs.
"Neither Iran, nor our friends in the region or any other country in the world can decide for the Syrian people," he was quoted by the official Islamic Republic News Agency as saying.
Iran is considered one of Syria's strongest allies. Iranian Foreign Minister Ali Akbar Salehi this week said he was troubled by reports that Syrian opposition forces had used chemical weapons. Other groups have blamed the Syrian government for chemical weapons use.
U.N. Secretary-General Ban Ki-moon said he supports an investigation into the claims, though the Syrian government said it was suspicious of any eventual probe.
Abdollahian said Iran was concerned that the United States had "engineered" the revolution in Syria. He accused the United States of sending al-Qaida forces into Syria, but said they've since realized it was a mistake given the lessons learned from the Afghan engagement.
Some of the Syrian rebel groups are aligned with al-Qaida. The U.S. government has designated those groups as terrorist organizations.