China's new J-20 stealth jet. Chinese Military Review BEIJING (Reuters) - China wants to step up cooperation with Iran's air force, the head of the Chinese air force told his Iranian counterpart on Monday, the latest in a series of high-level military contacts.

Ma Xiaotian told Hassan Shah Safi that relations between the two air forces had developed smoothly.

"(We) hope that cooperation can go up another level," Ma said, according to a statement issued by China's Defence Ministry, which did not elaborate.

A senior Chinese admiral visited Tehran last month and last year, for the first time ever, two Chinese warships docked at Iran's Bandar Abbas port to take part in a joint naval exercise in the Gulf and an Iranian admiral was given tours of a Chinese submarine and warships.

China and Iran have close diplomatic, economic, trade and energy ties, and China has been active in pushing both the United States and Iran to reach agreement on Iran's controversial nuclear program.

Under a multilateral deal, agreed in July, sanctions imposed by the United States, European Union and United Nations will be lifted in return for Iran agreeing to long-term curbs on a nuclear program that the West has suspected was aimed at creating a nuclear bomb.