China has said it will conduct "routine" naval exercises in the Pacific Ocean, in the week after a major diplomatic campaign by US President Barack Obama to assert the United States as a Pacific power.

The defence ministry said the exercises, to be held later this month, did not target any particular country, but the announcement comes against a background of growing tensions over maritime disputes in the Asia-Pacific region.

Obama, who has dubbed himself America's first Pacific president, said last week the US would deploy up to 2,500 Marines to Australia and tighten air force cooperation, a move seen as a response to China's growing regional might.

China's freedom of navigation "shall not be subject to any form of hindrance", the defence ministry said in a brief statement late Wednesday announcing the naval exercises in the western Pacific.

"This is a routine drill arranged under an annual plan, does not target any particular country or target, and complies with relevant international laws and international practice," it added.

Obama flew home Saturday after a seven-day tour of Pacific nations during which he took in a trio of summits and announced greater military involvement in the region.

"Here is what this region must know. As we end today's wars, I have directed my national security team to make our presence and missions in the Asia-Pacific a top priority," the US president announced during a visit to Australia.

Washington's new diplomatic campaign to assert itself as a Pacific power has alarmed China, which sees initiatives like stationing Marines in Australia as intruding into its sphere of influence.

China's Premier Wen Jiabao has warned against interference by "external forces" in regional territorial disputes including in the South China Sea, a strategic and resource-rich area where several nations have overlapping claims.

China claims all of the maritime area, as does Taiwan, while four Southeast Asian countries declare ownership of parts of it, with Vietnam and the Philippines accusing Chinese forces of increasing aggression there.

The competing claims have led to periodic outbreaks of tension between China and its neighbours in recent years, including with the Philippines and Vietnam in recent months, and with Japan in late 2010.

China's People's Liberation Army, the largest armed force in the world, is primarily a land force, but its navy is playing an increasingly important role as Beijing grows more assertive about its territorial claims.

Earlier this year, the Pentagon warned that Beijing was increasingly focused on its naval power and had invested in high-tech weaponry that would extend its reach in the Pacific and beyond.

Recent trials of China's first aircraft carrier underlined the scale of Beijing's naval ambitions, sparking jitters in the United States and Japan.

China, which publicly announced around 50 separate naval exercises in the seas off its coast over the past two years -- usually after the event -- says its military is only focused on defending the country's territory.

Arthur Ding, a Taiwan-based expert on the PLA, said China's navy conducted regular drills in the western Pacific, but that the timing of the latest announcement could be significant.

"We need to watch what kind of military exercise this fleet is executing. If it is a simple tactical drill, it can be said that this exercise aims to protest President Obama's recent statement, because it takes time to prepare a real exercise," he told AFP.

Asia-Pacific leaders held talks on the disputed territories at a summit Saturday, in a major diplomatic coup for the US, which had pushed for the topic to be raised, despite objections from Beijing.

China's official comments on Obama's trip were muted, but state news agency Xinhua said Asian suspicions would be raised by the plan to base troops in Australia and by US Secretary of State Hillary Clinton's declaration that the 21st century will be "America's Pacific century".

"If the US sticks to its Cold War mentality and continues to engage with Asian nations in a self-assertive way, it is doomed to incur repulsion in the region," the agency said.

"The hard fact is that the Pacific Ocean belongs to all countries sharing its shores, not just the United States."