The Chinese navy deployed two missile frigates on Thursday to expel a US Navy warship sailing close to China's Nansha Islands without permission, a Ministry of Defense spokesman said.

Guide-missile frigates Liuzhou and Luzhou were deployed to identify and warn the USS Dewey that entered waters of China's Nansha Islands to leave, ministry spokesman Ren Guoqiang said at a regular news conference.

Foreign media reported that the USS Dewey sailed less than 12 nautical miles from the Meiji reef of the Nansha Islands on Thursday morning, the first such practice under the administration of Donald Trump.

"China has undisputable sovereignty over the Nansha Islands and their surrounding waters," Ren said. "We strongly oppose such practice of the US military, which shows off its might, promotes regional militarization and easily causes unexpected air and sea accidents."

He said that China has made solemn representations to the US side over the matter.

Thanks to the joint efforts of China and ASEAN countries, the situation in the South China Sea is cooling down and showing positive signs of development, Ren said.

"But the wrong practice of the US side disrupts the improving situation and goes against the peace and stability of the South China Sea," he added.

Ren said healthy and steady military relations between China and the US are in line with the common interests of two countries, and it needs the concerted efforts of both sides.

"We urge the US to take concrete measures to correct the mistake and inject positive energy into the development of bilateral military relations," he said.

"Such wrong conduct of the US military will only encourage the Chinese army to further strengthen its capacity building and firmly defend our national sovereignty and security," Ren said.