"The importance of the Asia-Pacific to the future of the US I don't think can be overstated," Xinhua quoted US Air Force Geneneral Herbert Carlisle as saying at the Centre for Strategic and International Studies here.
It has been more than two years when the US announced its Asia-Pacific strategic re-balance, which includes plans to deploy 60 percent of its warships to the region by 2020 and an increase in American troop rotations there.
Carlisle noted that for Asian-Pacific nations dealing with territorial or internal disputes, Russia's intervention in neighbouring Ukraine and its annexation of Crimea are causing increasing concerns.
"What Russia is doing in Ukraine and Crimea has a direct effect on the Asia-Pacific," he said, adding that Russia is becoming "increasingly active" in the Pacific, where the country has a long Eastern border, making its actions "a challenge for us in the Asia- Pacific as well as Europe."
As area air defence commander, Carlisle's command of 45,000 Pacific Air Forces airmen has him overseeing security for more than half the planet's surface and the world's five largest economies, as well as 60 percent of the planet's population.
"You can fit every land mass on the planet in the Pacific Ocean and still have room left over for another North American continent and another African continent," the general noted.
Last year's federal budget sequester had the effect of slowing down the number of US military regional engagements, Carlisle said, but that has since picked up, with the total number set to be about 400 this year. But he warned that the challenges to regional security continue to exceed the capacity of the US.