U.S. Vice President Kamala Harris called out Beijing's behavior on the South China Sea on Tuesday.
Speaking in Singapore, she accused China of using intimidation to back unlawful claims of territory.
“In the South China Sea, we know that Beijing continues to coerce, to intimidate and to make claims to the vast majority of the South China Sea. Beijing's actions continue to undermine the rules-based order and threaten the sovereignty of nations.”
An international tribunal in 2016 rejected China’s claims along a so-called Nine Dash Line, which goes through waters also claimed by Brunei, Malaysia, the Philippines and Vietnam.
China rejected the ruling and has established military outposts on artificial islands.
The South China sea is vital for shipping and is rich in natural resources.
"There should be no doubt we have enduring interests in this region, and we have enduring commitments as well. Those commitments include of course security."
The U.S. Navy regularly conducts what they call “freedom of navigation” operations.
China objects to them, saying they don't help regional peace or stability.
Last month, a top Chinese diplomat accused the U.S. of creating an “imaginary enemy,” diverting attention from domestic issues to, instead, suppressing China.
Harris is on seven-day tour of Southeast Asia.
Part of her task there is convincing leaders that the U.S. remains committed to the region, with doubts after leaving behind chaos in Afghanistan from its evacuation efforts.
Harris suggested the U.S. host the 2023 meeting of APEC, the Asia-Pacific trade group, which includes the U.S., China and Japan.