With tensions high in the South China Sea, China announced Thursday that Russia would enter the fray and the two nations would conduct naval drills in the contested waters in September.

“This is a routine exercise between the two armed forces, aimed at strengthening the developing China-Russia strategic cooperative partnership,” said China's defense ministry spokesman Yang Yujun during a news conference, Reuters reported. “The exercise is not directed against third parties.”

China and Russia have held joint exercises in the past in the Sea of Japan as well as the Mediterranean Sea. Yang said the two nations had already held exercises this year meant to help maintain “global peace.” The exercises in September will be the first in the South China Sea for the two nations, the Wall Street Journal reported.

South China Sea Chinese ships are seen during a search and rescue exercise near Qilian Yu subgroup in the Paracel Islands, which is known in China as Xisha Islands, South China Sea, July 14, 2016. Photo: Reuters/Stringer

The exercises will include both air and sea drills, the Associated Press reported. Exacts locations for the drills were not provided during the news briefing.

The Permanent Court of Arbitration in the Hague ruled earlier this month that China’s expansive claims in the South China Sea were not legal and not based on any historic claims. Beijing has rejected the court’s ruling with Chinese President Xi Jinping saying islands in the South China Sea have been “Chinese territories since ancient times.” Russia has supported China’s rejection of the court ruling.

The joint exercises come as the U.S. continues its freedom of navigation patrols in the waters and Moscow’s influence in the American presidential election is under scrutiny after officials pointed to the Kremlin for being behind a hack of the Democratic National Convention. 

China has blamed the U.S. for causing heightened tensions in the contested waters with its patrols. Both Moscow and Beijing remain at odds with American foreign policy and have become allies on the United Nations Security Council where all three nations hold permanent seats.

Brunei, China, Malaysia, the Philippines, Taiwan and Vietnam have all laid claim to parts of the contested waters of the South China Sea. Over $5 trillion worth of trade passes through the resource rich waters every year.