Iran says it welcomes a U.S.-Russian agreement on a cease-fire for Syria, where it has been a key ally of President Bashar Assad during the five-year war.

Iran's semi-official ISNA news agency on Sunday quotes Foreign Ministry spokesman Bahram Ghassemi as saying that "Iran has always welcomed a cease-fire in Syria and the facilitation of humanitarian access to all people in this country."

The deal is set to go into effect on Monday night. Both Assad's forces and the U.S.-backed rebels would cease attacks, while the U.S. and Russia would join forces against Islamic State and al-Qaida-linked militants.

Iran, along with Russia, is a key ally of the Syrian government. Tehran has sent some of its top military commanders, as well as Revolutionary Guard forces, to bolster Assad's troops.