Iran stands fully behind Syria and blames the United States and Arab nations for the bloody unrest shaking its ally, media on Monday quoted a deputy foreign minister as saying.
"The Islamic Republic of Iran underlines its total support for the Syrian people and government," Hossein Amir Abdollahian said, according to Iran's official IRNA news agency.
He said Western and Arab nations "that support the insecurity and instability in Syria are responsible for any aggravation of the crisis in Syria."
Amir Abdollahian said Iran continues to believe in a "political solution" based on reforms agreed to by Assad.
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In a separate interview to Russian media picked up by the Iranian daily Kayhan, the deputy foreign minister said: "The troubles in Syria are happening with the backing of the United States, European and Arab countries with the massive delivery of weapons to the country."
Iran, the principal Middle East ally of Assad's government, has denied US allegations it is sending arms to Syria to help put down the uprising there.
It has also voiced its opposition to any military intervention in Syria.
A diplomatic clash is brewing over the situation in Syria among UN Security Council members. Russia and China have already twice vetoed resolutions condemning the violence.
UN-Arab League peace envoy Kofi Annan left Damascus on Sunday without managing to secure an accord to end bloodletting in Syria, as fighting raged in major flashpoints leaving dozens more dead.