BEIJING — In a show of strength before an international court’s ruling on China’s claims in the South China Sea, the United States Navy sent two aircraft carriers and their accompanying ships on training drills in the western Pacific Ocean on Saturday.
The carriers John C. Stennis and Ronald Reagan sailed close together in the Philippine Sea as part of air defense and sea surveillance operations that involved 12,000 sailors, 140 aircraft and six smaller warships, the United States Pacific Fleet in Hawaii said in a statement.
“We must take advantage of these opportunities to practice war-fighting techniques that are required to prevail in modern naval operations,” Rear Adm. John D. Alexander said in a statement.
The operations occurred on the eastern side of the Philippines, in a body of water that is not adjacent to the South China Sea but is close, a spokesman for the Pacific Fleet said. China seeks to dominate the western Pacific Ocean as part of its long-term strategy, American strategists say.
The message of the exercise by the two carriers and their attendant warships was unmistakable, and the timing was deliberate, said an American official familiar with the planning of the operation who spoke on the condition of anonymity because he was not authorized to speak publicly on the matter. It could have been conducted later, he said.
An international arbitration court in The Hague is deliberating a case filed by the Philippines in 2013 against China’s claims in the South China Sea, and its decision is expected in the coming weeks.
The Philippines is challenging China’s claims to what has come to be known as the nine-dash line, an area that covers almost all of the South China Sea, including waters close to the Philippine coast.
The issue of the nine-dash line is delicate because China has claimed it since ancient times as its territory, and the South China Sea has become part of the increasingly nationalistic vocabulary of President Xi Jinping.
In the past two years, China has built artificial islands equipped with military runways in the Spratly archipelago, inside the line and not far from the Philippines.
In a statement on the exercise involving the carriers, the Pacific Fleet said: “As a Pacific nation and a Pacific leader, the United States has a national interest in maintaining security and prosperity, peaceful resolution of disputes, unimpeded lawful commerce, and adherence to freedom of navigation and overflight throughout the shared domains of the Indo-Asia-Pacific.”
The Stennis conducted exercises with Japanese and Indian naval forces in the western Pacific and the South China Sea earlier in the week, an operation that was shadowed by a Chinese surveillance vessel.
The Stennis then joined the Reagan, which had been undergoing maintenance at a United States base in Japan, the Pacific Fleet spokesman said.
Early this month, Senator John McCain, Republican of Arizona and the chairman of the Senate Armed Services Committee, foreshadowed the dual-carrier exercise during a speech in Singapore, saying it was part of the United States’ increased vigilance in the Pacific.
“The United States will soon have two aircraft carriers operating together in the Pacific, which is a strong statement about America’s enduring commitment to regional security,” Mr. McCain said.
Also this past week, the United States dispatched four Navy electronic attack aircraft, known as Growlers, and 120 military personnel to Clark Air Base in the Philippines.
At a conference in Beijing on Saturday hosted by Global Times, a state-run newspaper known for its strident coverage, some analysts warned of an arms race in the western Pacific.
“The Chinese side is determined to increase its power, and Obama is determined to defend the United States’ position,” said Shi Yinhong, a professor of international relations at Renmin University in Beijing.
Both militaries need to be cautious in the South China Sea, said another participant, Teng Jianqun, the director of the department of American studies at the China Institute of International Studies. “Any misunderstanding could lead to a disaster between the two countries,” Mr. Teng said.