Thousands of US soldiers will begin nearly two weeks of war games in the Philippines on Monday as the two nations look to strengthen their military alliance amid concerns over China's rising power.

The Balikatan (Shoulder-to-shoulder) exercises are an annual event but this year are expected to attract a greater focus with some of the drills set to be held close to sensitive South China Sea waters claimed by the Chinese.

The Philippines insists the exercises, involving 4,500 US personnel and 2,300 Filipino troops, should not be seen by China as a provocation.

"Our aim is not against any country, our aim is to protect maritime security and to protect the interests of our country," Major Emmanuel Garcia, Philippine military spokesman for Balikatan, told AFP.

Nevertheless, Garcia confirmed US and Philippine ships will stage drills in waters facing the South China Sea, while Filipino leaders have repeatedly said that China is one of the country's main "maritime security" concerns.

China claims all of the South China Sea as a historic right, even waters close to the coasts of the Philippines and other Southeast Asian countries.

The competing claims to the strategically vital waters have long made the area one of Asia's potential flashpoints for military conflict.

The Philippines has complained over the past two years that China has become increasingly aggressive in staking its claim to the waters, accusing the Chinese of acts such as firing warning shots at Filipino fishermen.

Tensions spiked again this month when Philippine and Chinese ships became locked in a standoff at a tiny set of islets called Scarborough Shoal in the South China Sea.

After nearly a week, both sides have refused to back down and are still keeping civilian vessels at the shoal, 230 kilometres (140 miles) west of the Philippines' main island of Luzon, in an effort to assert sovereignty.

Facing the perceived growing threat from China, Philippine President Benigno Aquino last year called for closer military ties with the United States.

The United States was the colonial ruler of the Philippines in the first half of the 20th Century and maintained military bases until the early 1990s, but was forced to end its permanent presence amid anti-US sentiment.

Aquino's appeal last year was welcomed in the United States, which has been seeking to rebuild its presence across the Asia Pacific, partly to counter the growing political, economic and military might of China.

Aquino told AFP last month that, although there would be no return to permanent US bases in the Philippines, he welcomed a greater American military presence through more joint exercises such as Balikatan.

In this context, Balikatan will hold extra significance in terms of sending a message to China, according to John Blaxland, a regional security and political expert from the Australian National University.

"It's a subtle message affirming for the Philippines that the US is serious about playing in Asia and will lend assistance to those in need," Blaxland told AFP.

The Balikatan exercises, which run from Monday until April 27, are scheduled to be held on Luzon as well as Palawan, a narrow island that forms the country's western-most landmass.

The Philippines and the United States have emphasised that Balikatan is not focused solely on conflict, with troops also set to conduct humanitarian and disaster-relief exercises.

Balikatan will be launched on Monday with opening ceremonies in Manila.