China’s military is paying “close attention” to an agreement between the United States and Singapore to deploy the U.S. P8 Poseidon spy plane to the city state and hopes the move does not harm regional stability, the defence ministry said.

“We are paying close attention to how the relevant situation develops, and hope bilateral defence cooperation between the relevant countries is beneficial to regional peace and stability and not the opposite,” the ministry said in a brief statement late on Tuesday.

The foreign ministry of China, which is at odds with Washington over the South China Sea, said on Tuesday the move was aimed at militarising the region.

In a joint statement after a meeting in Washington on Monday, U.S. Defense Secretary Ash Carter and Singapore Defence Minister Ng Eng Hen welcomed the inaugural deployment of the aircraft in Singapore from Dec. 7 to 14.

A U.S. defence official said further deployments in Singapore could be expected. The move comes at a time of heightened tensions in the South China Sea.

China claims almost the entire energy-rich waters, through which more than $5 trillion of maritime trade passes each year. The Philippines, Brunei, Vietnam, Malaysia and Taiwan have overlapping claims.

The United States already operates P8s from Japan and the Philippines, and has conducted surveillance flights from Singapore’s neighbour, Malaysia.

Washington has criticized China’s building of artificial islands in the South China Sea’s disputed Spratly archipelago, and has conducted sea and air patrols near them recently.

Last month, U.S. B-52 bombers flew near some of China’s artificial islands and at the end of October a U.S. guided-missile destroyer sailed within 12 nautical miles of one of them.

In May, the Chinese navy issued eight warnings to the crew of a U.S. P8 that flew near the islands, according to CNN, which was aboard the aircraft.