Russia’s Defense Minister Sergei Shoigu arrived on Sunday in Tehran for a surprise visit, Iran’s state television reported.
Shoigu is expected to meet President Hassan Rouhani and his counterpart Hossein Dehghan during his trip to discuss the “situation in the region,” it said.
The trip comes days after Dehghan visited Moscow on Tuesday, during which Shoigu said Russia and Iran were ready to step up their military cooperation.
Russia denied reports last week that it would start shipping the S-300 advanced air defense system to Iran, citing payment issues.
Russia and Iran are both longtime allies of Syrian President Bashir al-Assad’s regime.
Moscow launched air strikes in support of Syria’s government on September 30.
Tehran supports Assad by sending “military advisers” and volunteers to fight alongside the Syrian army.
Shoigu’s trip was announced as US Secretary of State John Kerry announced a provisional deal had been reached on a ceasefire that could begin in the next few days in Syria’s five-year civil war.
Kerry said he spoke Sunday morning with Russian Foreign Minister Sergey Lavrov to discuss terms of the ceasefire and the two now must reach out to the parties in the conflict.
He declined to go into the details of the agreement, saying it “is not yet done.” But he said he hoped US President Barack Obama and Russian President Vladimir Putin would talk soon and that after that, implementation could begin.
“The modalities for a cessation of hostilities are now being completed,” Kerry said. “In fact, we are closer to a ceasefire today than we have been. A cessation of hostilities … is possible over the course of these next hours.”