Iran’s navy kicked off the first joint naval exercise in the northern Indian Ocean with Russia and China on Friday, Dec. 27, Iranian state television reported.

The four-day drill, conducted from Chahbahar a southeastern port city in the Gulf of Oman and close to the border with Pakistan. It aims to improve the security of the region’s waterways, the report quoted Iran’s navy chief Adm. Hossein Khanzadi as saying.

China’s Defense Ministry spokesman Wu Qian said on Thursday that the exercise would “deepen exchange and cooperation between the navies of the three countries.” He said the Chinese navy’s guided-missile destroyer “Xining” was participating in the drill.

China has close diplomatic, trade, and energy ties with Iran, which has friendly ties with Russia.

Meanwhile, Moscow said it was an unprecedented exercise in naval cooperation and training. 

Russia’s Defense Ministry said it sent three ships from its Baltic Fleet on Friday—a frigate, a tanker, and a rescue tug boat—to participate in the drills, according to a Russia’s official military newspaper.

The ministry was quoted as saying that such drills are being held in such a format for the first time.

In the face of unprecedented economic sanctions from Washington, Tehran tried to step up military cooperation with Beijing and Moscow. Russian and Chinese naval representatives have also increased their visits to Iran in recent years.

Iranian television also said the drill shows Iran is not isolated, despite U.S. withdrawal from the 2015 nuclear deal with world powers.

“The message of this exercise is peace, friendship, and lasting security through cooperation and unity… and its result will be to show that Iran cannot be isolated,” Iranian flotilla Adm. Gholamreza Tahani said on state television.