Iran, China, and Russia began joint naval drills on Friday in the Indian Ocean and the Gulf of Oman, an Iranian naval spokesman said.
"The message of this exercise is peace, friendship and lasting security through cooperation and unity...
The broadcaster said the drills included rescuing ships on fire or vessels under attack by pirates and shooting exercises.
The Gulf of Oman is a particularly sensitive waterway as it connects to the Strait of Hormuz, through which about a fifth of the world's oil passes and which in turn connects to the Gulf.
Washington proposed a U
President Donald Trump last year pulled the United States out of Iran's 2015 nuclear deal with six nations and re-imposed sanctions on the country, crippling its economy.
Tension has risen in the region not only over Iran's disputed nuclear
China said on Thursday it was sending a guided-missile destroyer to the four-day drills, which it called a "normal military exchange" between the three armed forces.
"It is not necessarily connected with the regional situation," a Chinese defense ministry spokesman said.
China has close diplomatic, trade and energy ties with Iran, which has friendly ties with Russia.
Both Russia and China also have good relations with Iran's regional rival Saudi Arabia.