Options are on the table to fly surveillance aircraft and sail Navy ships nearby in a move that puts the U.S. directly into a contentious territorial contest in East Asia, in which, until now, the U.S. has avoided overtly taking sides.
The South China Sea is the subject of numerous rival -- often messy -- territorial claims, with China, Brunei, Malaysia, the Philippines, Taiwan and Vietnam disputing sovereignty of several island chains and nearby waters.
China on Wednesday cautioned the U.S. against taking any actions that might be considered provocative, according to a report from the state-run Xinhua news service.
While Beijing supports freedom of navigation in the South China Sea, the U.S. must be careful in how it uses that right, Chinese Foreign Ministry spokeswoman Hua Chunying said in the report.
"Freedom of navigation does not give one country's military aircraft and ships free access to another country's territorial waters and airspace," Hua is quoted as saying in the Xinhua report.
A U.S. Navy statement Wednesday said the littoral combat ship USS Fort Worth arrived for resupply in the Philippines after completing a weeklong patrol in the South China Sea that took it near the disputed Spratly Islands.
The Navy said it was the first time an LCS, one of the newest vessels in the U.S. fleet, had operated in international waters near the islands. The Spratlys have been claimed in whole or in part by China, Vietnam, the Philippines and Malaysia, according to the U.S. State Department.
"As part of our strategic rebalance to bring our newest and most capable Navy platforms to the Indo-Asia-Pacific, (the LCSs have) a regular presence in Southeast Asia. Routine operations like the one Fort Worth just completed in the South China Sea will be the new normal as we welcome four LCSs to the region in the coming years," Capt. Fred Kacher, commodore of the Navy's Destroyer Squadron 7, said in the Navy release.
The Navy said the Fort Worth came across "multiple" Chinese warships during its patrol. A photo released by the Navy showed the Fort Worth being trailed by a Chinese guided-missile frigate, the Yancheng.
"Our interactions with Chinese ships continue to be professional," the commander of the Fort Worth, Cmdr. Matt Kawas, said in the statement.
Kawas said his vessel followed the international Code for Unplanned Encounters at Sea to "clarify intentions and prevent miscommunication" with the Chinese ships.
Tense trip for Kerry?
The potential deployment sets the scene for a tense trip to Beijing by Secretary of State John Kerry this weekend.
He's expected to meet with senior Chinese leaders
to discuss the planned visit to the United States of President Xi Jinping this fall.
A State Department official told Reuters news agency
that Kerry would leave China "in absolutely no doubt" about Washington's commitment to ensuring freedom of navigation and flight in the South China Sea.
Tensions over the Spratlys have increased in recent months as China has built facilities on five reclaimed-land sites
in the islands, including a 10,000-foot (3,050-meter) airstrip.
James Hardy, editor of Jane's Asia Pacific, told CNN in February that China was executing "a methodical, well-planned campaign to create a chain of air and sea capable fortresses across the center of the Spratly Islands chain."
The disputed areas in the islands include fertile fishing grounds and potentially rich reserves of undersea natural resources.
released last week by the International Crisis Group said that clashes among the claimants were "becoming more heated and the lulls between period of tension are growing shorter."
"The handling of the competing claims will set the tone for relations within East Asia for years. The cost of even a momentary failure to manage tensions could pose a significant threat to one of the world's great collaborative economic success stories," the report said.