About 9,000 troops from United States, Australia and the Philippines started a joint military exercise on Monday amid ongoing tensions in the Asia-Pacific region over the South China Sea.
Some 5,000 American troops are taking part in the 11-day exercises, along with nearly 4,000 Filipino soldiers and 80 Australian special forces.
The drills are part of the annual Balikatan military exercises between the US and Philippines. Australian troops have participated in the drills since 2014.
China has repeatedly criticized US military presence in the region and suspects the military drills are part of efforts to contain Beijing.
Washington and Manila say that the drills are not directed against China, and that they also focus on preparing for natural disasters and humanitarian crises.
The Philippines is also preparing to host US troops at five bases under a defense pact born out of US President Barack Obama’s policy of a "pivot" to the Asia-Pacific, a plan to reassert American influence in the region.
US Marine Lieutenant-General John Toolan, commander of the US Marine Corps in the Pacific, told reporters in Manila the exercises would help the allies improve maritime security and maintain regional stability.
“Our alliance is strong. The United States is committed to this relationship, and these are not empty words. . . . Peace in Southeast Asia depends on our cooperation,” Toolan added.
US Defense Secretary Ashton Carter will be the first Pentagon chief to observe the exercises when he arrives next week, underscoring the significance of the war games for both countries.
China claims nearly all of the South China Sea, despite partial counterclaims by Brunei, Malaysia, Taiwan, Vietnam and the Philippines. China is also locked in disputes with Japan and South Korea over the East China Sea.
In recent years, China has built major structures including radar systems and air strips over reclaimed reefs and outcrops.
Washington has sent bombers and warships on patrol close to the Chinese construction activity in recent months, infuriating Beijing.
China's Xinhua news agency warned "outsiders" against interfering in tense South China Sea territorial disputes as the drills began on Monday.
"The... exercises caps Manila's recent attempts to involve outsiders in (a) regional row," Xinhua said in a commentary. "However, a provocation so fear-mongering and untimely as such is likely to boomerang on the initiators," it added.