China says US warships entered waters without Beijing's permission

The relevant action by the US side infringed upon China's sovereignty, and undermined the peace, security, and order of the relevant waters, Hua said, adding that China will continue to take necessary measures to safeguard itself.

Hua Chunying, a foreign ministry spokeswoman, said the PLA Navy warned the USS Spruance and USS Preble against approaching Chinese-claimed territory in the Spratly Islands.

"Under such circumstances, the U.S. insistence on provocation, creating tensions and destroying the peace and stability of the South China Sea is unpopular", she said.

Vietnam, the Philippines, Brunei, Malaysia, Indonesia and Taiwan have competing claims in the region.

USA negotiators were in Beijing on Monday for another round of talks on a trade deal with the clock ticking towards a March 1 deadline set by President Donald Trump.

The Spratly Islands are a disputed group of islands, islets and cays and more than 100 reefs, sometimes grouped in submerged old atolls, in the South China Sea.

Speaking at a meeting of the Atlantic Council in Washington last week, Admiral John Richardson, chief of US Naval Operation, called for firmer rules governing naval encounters in disputed waters such as the South China Sea.

Navy spokesman Commander Clay Doss told U.S. media: "All operations are designed in accordance with global law and demonstrate that the United States will fly, sail and operate wherever worldwide law allows". The deployment is seen as the latest attempt by Washington to stand up to what it believes are attempts by Beijing to limit freedom of navigation in the strategic waters, where Chinese, Japanese and other Southeast Asian navies operate.

The rising military tension comes against the backdrop of an increasingly bitter trade war between China and the US.

The two countries have traded barbs over what United States said was Beijing's military installation building on artificial islands and reefs. The United States has criticised China for militarising the islands by constructing long runways used by jet fighters and deploying anti-aircraft missiles.

China defends its construction as necessary for self-defence and says it is the USA that is responsible for ratcheting up tensions in the region by sending warships and military planes close to islands Beijing claims.