Iran and China began a joint naval exercise in the Gulf on Sunday.

The military drill comes at a time of heightened tension between the Iranian and U.S. military in the Gulf and is likely to be a cause of concern for Washington.

In recent months, the U.S. navy has accused the Iranian navy of sending fast-attack boats to harass warships as they pass through the Strait of Hormuz.

An Iranian destroyer and two Chinese destroyers are among the vessels that will participate in the exercise, which will take place in the eastern portion of the Strait of Hormuz and the Sea of Oman, according to IRNA. Some 700 Iranian navy personnel will be participating in the drill.

Two Chinese warships docked at Iran's Bandar Abbas port to take part in a joint naval exercise in the Gulf for the first time in 2014.