The fast increasing military might of China is a growing concern for the US, a top Pentagon official said."Having just visited China recently, certainly both South Korea and Japan; we're all concerned with sustaining continued stability in the region," Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, said at a news conference here in Washington. "There is concern throughout the region with the growth of China, the pace that they're growing their defence, the capabilities which in many cases are what we call anti-access: They'd like to see the United States stay out. And we're addressing those issues with China," he said. Mullen, who recently visited China, said, "I'm delighted, quite frankly, that my counterpart came here and I was able to go there, and we could restart military-to-military relationship, so we can have these discussions, because there are going to be some other rough times."I just hope we can sustain that relationship, and build on it over time.""But it's an area of great concern, certainly growing concern as China builds," Mullen said at a joint news conference with the Defence Secretary Leon Panetta. "And what we speak to when we're talking to China is transparency. What's your strategy? Why are you building this? Typically the answer is defensive. We certainly see other capabilities that are not just defensive," he said.The unity of the countries in the region with respect to the South China Sea is very important. "You've seen that. We need those disputes to be settled peacefully and, again, to support stability in the region. And that's what we're focused on," Panetta said in response to a question on China.He said North Korea certainly has historically generated provocations and the South Korea basically has taken a strong position. "They're not going to tolerate that anymore.""South Korea is a tremendously strong, long-standing ally that we are very supportive of, and we continue to work with them to try to ensure that stability. And that's a lengthy discussion I had when I was in China with my counterpart," he said.