Iran and Syria signed a deal for military cooperation in a meeting between the defence ministers of the two countries in Damascus, the Tasnim news agency reported on Monday.
Iranian Defence Minister Amir Hatami travelled to Damascus on Sunday for a two-day visit, meeting Syrian President Bashar al-Assad and senior military officials, Tasnim reported.
Iranian forces have backed Assad in the country's civil war.
Tasnim did not provide any details about the military cooperation deal.
US National Security Adviser John Bolton said last week that Iran should remove its forces from Syria.
Senior Iranian officials have said their military presence in Syria is at the invitation of the Assad government and they have no immediate plans to withdraw.