U.S. Defense Secretary Ash Carter said he will visit a U.S. aircraft carrier transiting the disputed South China Sea on Friday, a move bound to anger China, which has been increasingly asserting its territorial claims.
Carter made a similar visit to another U.S. aircraft carrier in November as it was crossing the South China Sea.
Carter was speaking at the close of joint U.S.-Philippines "Balikatan" military exercises in Manila. Sailors and Marines from the USS John C. Stennis carrier, the vessel Carter will visit, took part.
China claims almost the entire South China Sea, believed to have huge deposits of oil and gas. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims to parts of the waters, through which about US$5 trillion (£3.54 trillion) in trade is shipped every year.
"With each Balikatan and each cruise by the Stennis, with each new multilateral exercise and each new defence agreement, we add a stitch to the fabric of the region’s security network," Carter said in prepared remarks. "This is the network - peaceful, principled, and inclusive - America continues to stand for, and stand with."
Though not unprecedented, it was still a visit likely to inflame tensions with China, which says the United States is "militarizing" the South China Sea and endangering security.
The United States has already conducted what it calls "freedom of navigation" patrols in the area, sailing within 12-nautical mile territorial limits around disputed islands controlled by China to underscore its right to navigate the seas.
Those patrols have drawn sharp rebukes from China, but U.S. officials have said the United States will continue to challenge what it considers unfounded maritime claims.
Plans announced in Manila on Thursday to deepen U.S.-Philippine military ties, including joint patrols in the South China Sea, reflect a "Cold War mentality", China's Defence Ministry said, pledging to oppose any infringement on the country's sovereignty.
The carrier stop caps off a trip to Asia this week designed to highlight the expanding partnerships the United States is building with countries in the region, which Carter said had been asking for a greater U.S. role amid anxieties over China's actions.
"We will continue to stand up for our safety and freedoms, for those of our friends and allies, and for the values, principles, and rules-based order that has benefited so many for so long," Carter said.
Hundreds of U.S. troops and some aircraft will stay behind in the Philippines temporarily, and on Thursday, the two countries revealed they had begun conducting joint patrols in the South China Sea.
Australian Prime Minister Malcolm Turnbull told reporters in Beijing that economic gains in Asia had been based on a "foundation of peace and stability" and were the engine room of growth for the whole world.
"So that is why, with respect to the South China Sea, we urge all claimants to settle territorial disputes peacefully and in accordance with international law."