China and Russia said Monday that the South China Sea dispute should not be internationalized and called for its settlement based on negotiation and consultation, Beijing’s official Xinhua News reported. The comments come at time when the United States has beefed up its military presence in the contested region in a bid to help the Philippines and other Southeast Asian countries tackle China’s assertiveness.

Chinese Foreign Minister Wang Yi and his Russian counterpart Sergey Lavrov made the comments during a meeting on Monday. Wang insisted that China was protecting its rights and interests in South China Sea, and was free to choose how to resolve tensions in the area, Xinhua reported. The world’s second largest economy’s refusal of the Philippines’ proposed international arbitration case over the matter was meant to uphold the dignity and authority of the law, Wang said, adding that China and Russia should be cautious against abuses of mandatory arbitration.

Meanwhile, Hugo Swire, the British minister of state responsible for East Asia, said earlier in the day that a ruling — expected in May or early June — in the Philippines’ international arbitration case against China's South China Sea claims must be binding.

“We make it clear to the Chinese that we can only do these kinds of deals in an open and transparent way under an international rules-based system,” Swire told Washington's Center for Strategic and International Studies think tank, according to Reuters.

“Under the international rules-based system on which the world depends, we would expect the ruling from The Hague to be adhered to by all parties concerned, whichever way it goes and we would stand by others, including the United States, whichever way that ruling goes,” Swire added.

The South China Sea has been long debated, with Beijing laying claims to most of the region. Apart from China, Brunei, Malaysia, the Philippines, Taiwan and Vietnam have also laid claims to the waters. Beijing has been expanding its presence in the disputed region and has built three runways on the Spratly archipelago. China has consistently defended its actions, saying it does not have any intentions of starting a conflict and that its aircraft facilities will maintain safety in the region.

On Sunday, a Chinese military aircraft made the first public landing on the Fiery Cross Reef of the South China Sea. China’s official People’s Liberation Army Daily said that the aircraft was sent by the navy after receiving an emergency call from the construction site on the reef.  However, the move attracted a protest from the U.S. military Monday.

“We’re aware that a Chinese military aircraft landed at Fiery Cross Reef on Sunday in what China described as a humanitarian operation to evacuate three ill workers,” Pentagon spokesman Capt. Jeff Davis told CNN. “It is unclear why the Chinese used a military aircraft, as opposed to a civilian one.”

The Philippines and the U.S. conducted joint patrols in the South China Sea. The Pentagon will reportedly deploy six aircraft and three helicopters with 200 pilots and crew members at the former Clark Air Base, north of Manila. The aircraft fleet includes five Warthog ground-attack planes, three search-and-rescue helicopters and a plane regularly in use to transport Special Operations forces.