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.