AS the United States begins harsh cutbacks on defence programs, an Admiral has expressed alarm at China's 11 per cent spending boost.

The budget cuts are starting to affect United States military activities in the Asia-Pacific and threaten to undermine Washington's strategy to rebalance its forces in the region, the US Pacific commander said this morning.

At the recent National People's Congress, China unveiled an 11 per cent increase in its 2013 military budget. It has recently unveiled a large list of new aircraft, frigates and aircraft carriers in a move that has made Pacific nations such as Japan and the Philippines nervous.

The US military spending still far exceeds any other nation's - its budget is likely between two and three times bigger than China's - but defense chiefs complain about the across-the-board nature of the latest cuts.

The cuts are crimping plans to "pivot" to Asia, championed by the Obama administration as US has withdrawn from wars in Iraq and now Afghanistan. It's a strategy that has been broadly welcomed in a region unnerved by China's assertive behavior in disputed territories and its military buildup.

Admiral Samuel Locklear told a congressional panel that in the near-term, cuts will affect training, ship deployments and exercises with US allies such as Australia. He likened the longer-term effect to an avalanche that will gain momentum.

media_camera Chinese J-10 fighter jets taxiing past an Air Force officer on the tarmac at the Yangcun Air Force base of the People's Liberation Army Air Force in Tianjin, home of the 24th Fighter Division, southeast of Beijing.

Locklear said for regional stability and safeguarding US interests in a sprawling region of vital economic importance, "We have to get it right in the Asia Pacific."

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"So we have a plan for rebalance," Locklear told the House Armed Services Committee. "The road we're on will undermine that."

From the start of March, automatic cuts to defense and other areas of government have taken effect because of a failure by Republicans and Democrats to agree on a plan to trim the nation's vast debt. Unless a compromise is reached, the cuts could be extended for another nine years.

Locklear underscored U.S. intent to have a cooperative relationship with China rather than contain its emergence as a global power.

But when asked, Locklear did express concern about the growth in China's submarine fleet, which he said was forecast to grow to the high 70s or 80, which will be more than the US has to operate in the Pacific.

"The growth of the Chinese submarine force is a little bit puzzling to me in both its size and its sophistication," he said.

Locklear, who is based in Hawaii, commands some 330,000 military personnel, operating from waters off the west coast of the US to the western border of India.

media_camera This file image shows China's new stealth fighter jet, the J-20, the country's first radar-evading combat aircraft, during one of the many test runs at the military airbase in Chengdu, southwest China's Sichuan province.

Originally published as Admiral's alarm at China's strength