China Russia naval exercise in the Yellow Sea.

Four Russian warships, as well as support vessels, warplanes, helicopters and naval infantry, will team up with Chinese naval forces in a joint exercise in April, a source in Russia’s Pacific Fleet said on Tuesday.

The Russian Navy will be represented by the guided missile cruiser Varyag, and three large antisubmarine ships in an exercise that is to take place between April 22 and 29 in the Yellow Sea.

In all, more than 20 Russian and Chinese warships and support vessels will participate.

Since 2005, China and Russia have conducted several joint military exercises within the framework of the Shanghai Cooperation Organization.

The group also includes the Central Asian countries of Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan and aims to promote regional cooperation and check U.S. influence.