Tensions between the US and China heightened again as the US Navy sending a warship into contested waters. China has said the ship violated its territory but the US says it is maintaining open shipping lanes.
China strongly condemned the United States for deliberately sailing a warship within 12 nautical miles of a disputed South China Sea island, which Beijing claimed as its own.
China's Defense Ministry spokesman Yang Yujun called the US action, "very unprofessional and irresponsible for the safety of the troops of both sides, and may cause extremely dangerous consequences."
Chinese armed forces will take whatever measures "necessary to safeguard China's sovereignty and security, no matter what provocations the US side may take," Yang said.
At issue is whether China, or other claimants to the islands, which also include The Philippines, Malaysia and Brunei, can choke off international shipping by demanding advanced notice of passing vessels in a part of the ocean that sees more than $5 trillion worth of trade pass through it every year.
China, which maintains de facto - though not necessary de jure - control over the territory, was the only claimant to complain about the US passage.
China slams US action
Separately, China's Foreign Ministry said, "The American warship has violated relevant Chinese laws by entering Chinese territorial waters without prior permission, and the Chinese side has taken relevant measures including monitoring and admonishments."
The US move was clearly aimed at China. The Beijing government has angered its Asian neighbors and increased tensions with the United States with its massive build-up of manmade islands in contested areas, which include the Paracel and Spratly islands.
Vietnam's Foreign Ministry spokesman Le Hai Binh said that his country respects "innocent passage" of ships through territorial waters in line with international law.
Citing historic grounds, China has laid claim to almost the entire South China Sea and its islands, reefs and atolls.
Davis said the United States was interested in maintaining free navigation and was not getting involved in sovereignty claims in the South China Sea.
"We do take a strong position on protecting the rights, freedoms and lawful uses of the sea and airspace guaranteed to all countries," he said. "All maritime claims must comply with international law."