US Secretary of State Hillary Clinton has said the US will get more involved in the Asia-Pacific region as it pulls out of Afghanistan and Iraq - building trade ties, reinforcing alliances and continuing to press for democratic reforms in authoritarian nations like China and Vietnam. At a summit in Hawaii, Clinton spoke at length about China and the need for the two nations to work together to ensure "strong, sustained and balanced future global growth". She declared her "alarm" over the recent self-immolation of 11 Tibetan monks and nuns in protest of Chinese policy. It is the strongest US wording so far on these incidents. "We have made very clear our serious concerns about China's record on human rights," she said. The US secretary of state addressed Hawaii's political leaders, heads of a dozen Pacific island nations and senior US military officials after arriving for the Asia-Pacific Economic Co-operation (Apec) summit. She said the winding down of the wars in Iraq and Afghanistan allowed the US to refocus on the Asia-Pacific. "After a decade in which we invested immense resources in these two theatres we have reached a pivot point," she said. "We now can redirect some of those investments to opportunities and obligations elsewhere. And Asia stands out as a region where opportunities abound. "It is becoming increasingly clear that in the 21st century the world's strategic and economic centre of gravity will be the Asia-Pacific, from the Indian subcontinent to western shores of the Americas," Clinton said. "One of the most important tasks of American statecraft over the next decade will be to lock in a substantially increased investment, diplomatic, economic, strategic, and otherwise in this region." Clinton said it was critical to "engage and seize new opportunities" in the Asia-Pacific, which has nearly half of the world's population, several of the largest and fastest-growing economies and some of busiest ports and shipping lanes. She talked about the challenges, such as military buildups, concerns about nuclear weapons, natural disasters and greenhouse gas emissions. The US has 50,000 troops stationed in Japan and South Korea. "As this region changes we must change our force posture, to ensure that it is geographically distributed, operationally resilient, and politically sustainable," she said. "A more broadly distributed military presence provides vital advantages, both in deterring and responding to threats, and in providing support for humanitarian missions." Clinton said Americans may think that in financial tough times the US should be scaling back rather than reaching out to Asia. "This thinking is understandable but it is mistaken," she said. "What will happen in Asia in the years ahead will have an enormous impact on our nation's future."