By Sylvia Westall and Tom Perry
BEIRUT (Reuters) - Syrian President Bashar al-Assad signaled on Tuesday he expected more support from his top regional ally Iran in the wake of a nuclear deal that includes Western states that have backed the insurgency against him.
Rebels fighting Assad expressed concern that the deal would expand Iranian influence in the region at their expense.
Iran has provided military and financial support to Assad in the four-year-long conflict that has become a focal point for Shi'ite Iran's power struggle with the conservative Sunni Muslim monarchy of Saudi Arabia.
Assad, in a telegram congratulating Iran's supreme leader on the deal agreed with major powers on Tuesday, called it "a major turning point" in the history of Iran and the world.
"We are confident that the Islamic Republic of Iran will support, with greater drive, just causes of nations and work for peace and stability in the region and the world," Assad said to Iran's Supreme Leader Ayatollah Ali Khamenei, according to the text published by state news agency SANA.
Iranian military support for Assad has come in the form of its backing for the Lebanese political and guerrilla group Hezbollah, the deployment of Iranian military advisers, and the mobilization of Shi'ite fighters from elsewhere in the region.
A series of setbacks for Assad since late March triggered repeated statements of support from Iran. Assad ratified a new $1 billion credit line from Iran this month. Iranian President Hassan Rouhani said last month Iran would back the Syrian nation and government "until the end of the road."
In a separate message to Rouhani, Assad said the coming days will would see momentum in the "constructive role" played by Iran in supporting "the rights of people".
Rebels fighting Assad say Iranian support has been crucial to his survival. "This agreement will make the region more dangerous," said Iyad Shamse, leader of a rebel group in northern Syria called the Asala and Tanmieh Front.
"Our fears from this agreement are an increase in Iranian influence in the region and this is what is making Assad happy," he told Reuters.
The spokesman for an alliance of rebel groups in southern Syria said Iran was backing Assad with "all its force" at present, and he was worried U.S. pressure would not be enough to stop Tehran from entering in the war.
"We are worried," he said.
(Editing by Giles Elgood)