Iranian state television said that during his two-day visit, Assad will discuss with Iranian leaders bilateral ties and the situation in the region, in particular in Lebanon and Iraq.
U.S. officials have accused both Syria and Iran of helping stir up insecurity in Iraq by supporting insurgents and allowing militants to cross their borders.
The United States has also accused Syria, Iran, and Hezbollah, the Lebanese guerrilla group backed by those countries, of trying to bring down Lebanon's elected government.
Lebanese Prime Minister Fuad Siniora recently accused Iran of using its territory to wage a proxy battle against the United States.
Iranians demonstrating in support of Hizballah in Tehran on July 17 (epa)
'FOR THE SAKE OF LEBANON': The Islamic Republic of Iran has served as an ideological inspiration for Hizballah since the Lebanese militant group's creation in 1982, and Tehran acknowledges that it supports the organization morally and politically. "Yes, we are friends of Syria and Iran" Hizballah leader Hassan Nasrallah has said. "For 24 years we benefited from our friendship with Syria and Iran for the sake of Lebanon...." (more)