Nearly 7,000 American and Filipino soldiers began a 12-day military exercise in Manila on Monday amid wide suspicion of the annual drill's aim at containing China and growing concerns over the South China Sea.

The joint exercise, named "Balikatan" or "shoulder to shoulder", started with an opening ceremony attended by Philippine Armed Forces Chief General Jessie Dellosa and US Ambassador to the Philippines Harry Tomas at the military's general headquarters in Camp Aguinaldo. It will continue through April 27.

In a speech at the opening ceremony, Dellosa did not specifically mention China but stressed that the drill displayed strong US support for its ally.

"Given the international situation we are in, I say that this exercise, in coordination with all those we had in the past, (is) timely and mutually beneficial," Dellosa said.

"The conduct of this annual event reflects the aspirations to further relations with our strategic ally, a commitment that has to be nurtured, especially in the context of the evolving challenges in the region."

Shi Yinhong, a professor of US studies at Beijing-based Renmin University of China, said the US and the Philippines view China as the imaginary target, which is "very clear" judging by the training courses their militaries use.

"The number of participants and the training content suggest the US intends to deter China in the short term from imposing any possible military threat to the Philippines. As for the long-term significance, the regular drill certainly strengthens the strategic military alliance between Washington and Manila to contain Beijing in the South China Sea," Shi said.

The Philippine military said the venue of the training exercises includes the area of South China Sea off Palawan, where both forces will pursue amphibious exercises and gas and oil platform defense drills.

Prior to the exercise, Emmanuel Garcia, the Balikatan public affairs officer, said on Sunday that the exercise is not in anyway related to the standoff between Philippine and Chinese ships at the Huangyan Island in the South China Sea. He said the military training would be focused on maritime security and counter-terrorism. He stressed that the exercises are not directed at any country.

"The ongoing drill is merely one of the frequent joint exercises of the US and the Philippines. However, in such a sensitive area and at such a sensitive moment, the drill conducted by a country that has disputable claims with China and no other maritime threat speaks to a hidden motive for (the Philippines)," said Li Guoqiang, director of the Research Center of Chinese Borderland History and Geography in China's Academy Social Science.

Reiterating that the Philippines had violated China's sovereignty and triggered a standoff in waters off the Huangyan Island, which is an integral part of Chinese territory, Foreign Ministry spokesman Liu Weimin on Monday also said that China expects relevant countries to do more to deepen mutual trust and protect peace and stability in the region.

Shi said Beijing's attitude shows that China still puts the overall stability of the region first, although the moves by the US across the Asia Pacific will "raise strategic doubts" between Washington and Beijing.

"Maybe we need not to exaggerate the influence of the annually scheduled drill," Li said. "But its frequency, the escalating scale and the disregard of China's concerns are clearly violations of the Declaration on the Code of Conduct on the South China Sea, as well as the consensus reached by Beijing and Manila."

Xinhua and AFP contributed to this story.

wangchenyan@chinadaily.com.cn