Sitting in his office in Washington, Kurt Campbell, the United States' top diplomat for Asia, surveys a changing region and sees the need for a delicate American approach. 'What Asian countries want is for the US to walk a careful line,' says Campbell, Assistant Secretary of State for East Asian and Pacific Affairs. While Asian nations want to see evidence of an 'enduring commitment' to issues such as a regional solution to the South China Sea dispute and development on the Mekong, 'they in no way they want the United States to stoke tensions, or to create unnecessary tensions in the relations with China'. 'That's what we seek as well,' he said, shortly before embarking with his boss, US Secretary of State Hillary Rodham Clinton, on a seven-nation tour of Asia. That mission will be come with President Barack Obama's long-delayed trip to India, South Korea, Japan and Indonesia. Whether China will see it that way remains to be seen, given recent concerns over Clinton's statements on US interest in seeing a regional solution to South China Sea disputes and the Diaoyu Islands falling within the US-Japan mutual security pact. While the US played a key role in getting the South China Sea dispute back on the regional agenda, Campbell said the role of Washington - which has offered to facilitate talks - was ultimately 'ancillary' on the issue. 'There is a strong desire on the part of other Asean states that the next phase of diplomacy should be between Asean as a whole and China, and we support that 100 per cent,' he said. 'We're going to be involved and engaged going forward, but that engagement will change, necessarily.' As well as stressing the country's commitment after perceptions of neglect under the previous Bush administration, Campbell makes clear that part of the re-engagement effort is to ease fears that the US' time has passed. 'There are persistent concerns - we've seen them in the past and now - about whether the United States is engaged in some sort of structural decline. The good news is, we've seen this picture before, and we've been able to rise and meet those challenges, and prove the naysayers wrong. But those voices are certainly heard in Asia.' But the reassertion of American power and interests in Asia must have its limits, according to some US-based analysts. 'The US has to take a Goldilocks approach: not too hot, not too cold,' says Robert Sutter, an Asian studies professor at the School of Foreign Service at Georgetown University.