The recent rise of China as a regional and global power, including its substantial military modernisation and buildup, is a source of strategic uncertainty and potential friction, a top Pentagon commander has told US lawmakers.

"China's rise as a regional and global power, including its substantial military modernisation and buildup, is a source of strategic uncertainty and potential friction," Admiral Samuel Locklear, the commander of the US Pacific Command (PACOM), told a Senate Committee during a confirmation hearing on Thursday.

The China-US relationship, he said in written response to questions, has been an area of in-depth study and analysis by current commander and staff of PACOM.

"China's continued rise as a regional and global power, coupled with its pursuit of military technology and capability and its increasing propensity for challenging the territorial and maritime claims of other countries, particularly in the South China Sea and the East China Sea, has had an unsettling effect in the region and increased the prospects for miscalculation," Senator Joseph Lieberman, Chairman of the Senate Armed Services Committee said.

China, Locklear said, appears to be building the capability to fight and win short duration, high-intensity conflicts along its periphery.

"Its near-term focus appears to be on preparing for potential contingencies involving Taiwan, and to deter or deny effective intervention in a cross-strait conflict. Its modernisation efforts emphasise anti-access and area denial capabilities," he said.

The commander said that Beijing's growing focus on military missions other than war includes humanitarian assistance, non-combat evacuation operations, and counter-piracy support.

"Lastly, China is strengthening its nuclear deterrent and enhancing its strategic strike capabilities through the modernisation of its nuclear forces, and is improving other strategic capabilities, such as in space, counter-space, and computer network operations," he said.

Locklear said that in terms of regional security, China's economic growth has increased its international profile and influence, and has enabled its leaders to embark upon and sustain a comprehensive transformation of its military forces.

"The pace and scale of China's military modernisation, coupled with the lack of transparency, raise many questions, both within the United States and in the region as a whole, about China's future," he said. Locklear said his first priority will be to continue to maintain a credible deterrent posture and reassuring military presence in the Asia-Pacific.

"Next, we must both deter North Korean aggression and counter their proliferation activities," he said. The top US commander said that actively pursuing steady and measured military-to-military engagement will be one of his top priorities to deal with the situation.

"Lastly, while supporting our nation's strategic focus on the Asia-Pacific and sustaining the realignment and transformation processes already underway, we must also carefully shepherd and repeatedly assess progress toward desired force posture, ensuring we remain cognisant of evolving budgetary realities," he said.

Locklear said the US will remain steadfast in its efforts to mature the military-to-military relationship with China.

"Both China and the US have a strong stake in the peace and stability of the Asia-Pacific region. Building a cooperative bilateral relationship will reduce the likelihood of a miscalculation, increase the clarity of Chinese strategic intentions and encourage mutual engagement in areas of common concern," he said.