China and the United States have repeatedly traded barbs in the past over what Washington says is Beijing's militarization of the South China Sea by building military installations on artificial islands and reefs. Ms Hua said the ships entered the waters without China's permission and that Beijing has expressed firm opposition and dissatisfaction at the move.
Speaking about the most recent operation, Commander Clay Doss, a spokesman for the U.S. Navy's 7th Fleet, told CNN that the action was meant to "to challenge excessive maritime claims and preserve access to the waterways as governed by worldwide law".
"All operations are designed in accordance with global law and demonstrate that the United States will fly, sail and operate wherever worldwide law allows".
Cmdr. Clay Doss, U.S. Seventh Fleet public affairs officer, told Fox News in a statement: "Guided-missile destroyers USS Spruance (DDG 111) and USS Preble (DDG 88) conducted freedom of navigation operations (FONOPS) in the South China Sea".
Beijing sharply criticised the operation.
It has also accused the government of supporting technology theft as part of its broader development strategy, while in China there is a sense that the U.S. is using the trade war to contain the country's rise. The official said Monday's operation focused on Mischief Reef, a location claimed by China, Vietnam and the Philippines. Beijing rejected the ruling and the authority of the tribunal. In January, the destroyer USS McCampbell challenged China's claims to the Paracel Islands.
The US has accused Beijing of installing missiles and other military hardware on the disputed islands.
Monday's sail-by is the second United States freedom-of-navigation operation in the South China Sea this year.
The alleged incursion by two US warships into the internationally disputed waters of the South China Sea was the second such move within five weeks. American warships have also sailed through the strait separating mainland China from democratically run Taiwan.
China says the construction is necessary for defence, and it was the U.S. that was responsible for tensions by sending warships and military planes close to islands Beijing claims.
In October, the destroyer USS Decatur had to maneuver to avoid a collision with a Chinese warship that came within 45 yards of its bow.
President Donald Trump said he is open to letting a March 1 deadline to raise tariffs on Chinese products pass without penalty if the two sides are near an agreement, sending a conciliatory signal as talks to resolve a trade war between countries continue.
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