MOSCOW (AP) — Russian warships set off Monday to take part in a joint naval drills with China, an exercise that showcases increasingly close defense ties between the two countries as they face tensions with the United States.

The Russian Defense Ministry said the Varyag missile cruiser, the Marshal Shaposhnikov destroyer and two corvettes of Russia’s Pacific Fleet would take part in maneuvers in the East China Sea starting Wednesday.

The ministry said the Chinese navy planned to deploy several surface warships and a submarine for the exercise. Russian and Chinese aircraft will also take part in the drills, according to the ministry.

Moscow and Beijing have displayed their growing military cooperation in recent months.

In November, Tu-95 bombers of the Russian air force and Chinese H-6K bombers flew joint patrols over the Sea of Japan and the East China Sea. As part of the drills, the Russian bombers landed in China for the first time, and the Chinese bombers flew to an air base in Russia.

In September, China sent more than 2,000 troops along with more than 300 military vehicles, 21 combat aircraft and three warships to take part in a sweeping joint exercise with Russia. The maneuvers marked the first time that China sent forces from three branches of its military to take part in a single Russian drill, in what was described as a show of the breadth and depth of China-Russia mutual trust.

Defense cooperation between Moscow and Beijing has grown stronger since Russian President Vladimir Putin sent his troops into Ukraine on Feb. 24.

China, which has declared a “no limits” friendship with Russia, has pointedly refused to criticize Moscow’s actions, blaming the U.S. and NATO for provoking the Kremlin, and has blasted the punishing sanctions imposed on Russia.

Russia, in turn, has strongly backed China amid the tensions with the U.S. over Taiwan.