The two sides are trying to hammer out a deal ahead of a March 1 deadline when U.S. tariffs on $200 billion worth of Chinese imports are scheduled to increase to 25 percent from 10 percent.
China struck an upbeat note on Monday as trade talks resumed with the United States, but also expressed anger at a U.S. Navy mission through the disputed South China Sea, casting a shadow over the prospect for improved Beijing-Washington ties.
She urged the USA to cease the "provocative actions".
The same day the latest talks began, two US warships sailed near islands claimed by China in the disputed South China Sea, a USA official told Reuters.
Two Arleigh Burke-class destroyers - the USS Spruance and the USS Preble - conducted a freedom-of-navigation operation on Monday, sailing within 12 nautical miles of Chinese outposts in the contested Spratly Islands.
A spokesperson for the U.S. Navy's 7th Fleet confirmed the FONOP Monday afternoon with global media, stating that the operation was conducted "to challenge excessive maritime claims and preserve access to the waterways as governed by worldwide law".
The US labelled the Chinese warship's actions unsafe and unprofessional, while Beijing said the US was threatening the safety and sovereignty of China.
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The operation was the latest attempt to counter what Washington sees as Beijing's efforts to limit freedom of navigation in the strategic waters, where Chinese, Japanese and some South-east Asian navies operate. "That is true in the South China Sea as in other places around the globe", he said.
In mid-January, US and British warships conducted their first joint military exercises in the South China Sea since Beijing began building bases and air strips on islands.
The US and its allies periodically send planes and warships near South China Sea islands and reefs claimed by Beijing to signal their right under worldwide law to pass through the waters, invariably angering China.
"There's been sort of a steady increase", Admiral John Richardson, the US Chief of Naval Operations, told reporters earlier this month when asked about China's militarization of the area.
Escalating tensions between the United States and China have cost both countries billions of dollars and roiled global financial markets.
Vietnam, the Philippines, Brunei, Malaysia, Indonesia and Taiwan all have competing claims for territory in the region.