Starting Thursday, the Chinese and Russian navies shall be starting their largest-ever joint exercises, in the Pacific with more than 20 ships and will include anti-submarine operations as well as a joint-beach landing. The U.S. Navy is on alert with this development. The exercise titled "Joint Sea 2015 II" will start on Aug. 28 in the Sea of Japan and off the coast of Vladivostok.

USNI, The U.S. Naval Institute's online news and analysis portal, said that the forthcoming China-Russia exercises will be the second series of joint drills in less than a year. The first "Joint Sea 2015" operation was held in the Mediterranean Sea in April. Russian Defense Minister Sergei Shoigu said late last year that the U.S. was a factor motivating increased China-Russia military training, reports USNI. "We believe that the main goal of pooling our effort is to shape a collective regional security system. We also expressed concern over U.S. attempts to strengthen its military and political clout in the [Asia-Pacific Region]," Shoigu said in November.

A source close to the operation said the navies of the two countries will join forces to simulate anti-submarine combat and air defense and other relevant missions. A joint beach landing of troops is also planned. The source said the drills "are not targeted at any third party and are not relevant to regional status-quo."

"The drills are part of annual exchange program between Chinese and Russian militaries," the source said, according to Chinese state-controlled Xinhua news service.

The exercises mark the first time the Chinese Navy will take part in a joint operation in the Sea of Japan, bordering North and South Korea, Russia and Japan. The drills will take place in the Peter the Great Gulf, waters off the Clerk Cape and the Sea of Japan. Six helicopters, five fixed-wing aircraft, 21 units of amphibious equipment and 200 marines are said to be preparing to join the exercise from the Chinese side, with the Russian navy reportedly planning to send 16 surface ships, two submarines, 12 naval aircraft, nine amphibious vehicles and 200 marines, according to The Washington Times.