China's military is paying "close attention" to an agreement between the United States and Singapore to deploy the U.S. P-8 Poseidon spy plane to the city state and hopes the move does not harm regional stability, the defense ministry said.

"We are paying close attention to how the relevant situation develops, and hope bilateral defense 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 militarizing the region.