File photo: People pose for a group photo together after landing at the airfield on Yongshu Jiao in the Nansha Islands, Jan. 6, 2016. China successfully carried out test fights of two civilian aircraft on Jan. 6 on a newly-built airfield in the Nansha Islands of the South China Sea. (Xinhua file photo/Xing Guangli)

BEIJING, May 10 -- China on Tuesday expressed "resolute opposition" to a U.S. warship patrol in the South China Sea near Yongshu Jiao in the Nansha Islands.

The U.S. warship, USS William P. Lawrence, illegally entered China's waters near the islands on Tuesday without the permission of the Chinese government, Chinese Foreign Ministry spokesperson Lu Kang said, adding that the warship was monitored, tracked and issued with a warning.

It is reported that Bill Urban, the spokesman for U.S. Department of Defense, said the freedom of navigation operation was in direct challenge to "excessive maritime claims of some claimants in the South China Sea."

"The action by the U.S. threatens China's sovereignty and security, endangers the safety of people and facilities on the reef, and harms regional peace and stability," Lu said.

"China strongly opposes such action by the U.S. and will continue to take measures to safeguard our sovereignty and security," Lu said, adding China and other coastal states in the South China Sea have been working together to keep navigation and overflight free in the South China Sea for a long time. In fact, the freedom of navigation and overflight in the South China Sea has never been a problem.

According to Lu, the United States introduced freedom of navigation operations in 1979 before the signing of the UN Convention on the Law of the Sea (UNCLOS), a treaty to which the United States is still not a party. The purpose of these recurring "patrols" is to disrupt the order of the seas and oceans without adhering to the UN convention.

The United States sends military vessels and aircraft on surveillance missions against China as simple acts of provocation, said Lu, adding that the United States actually considers itself above the UNCLOS and these activities are opposed by many countries.

Lu said that the flexing of U.S. military muscle in the name of freedom of navigation is the biggest threat to peace and stability in the area.