Transcript for Ash Carter on Chinese President: 'He Needs To Be Good To His Word'
China and Taiwan in 66 years, it lasted a full minute. Opening talks to signal a new phase for those two countries. All of Asia and the U.S., as bob woodruff explains from his visit to the south China sea with defense secretary ash Carter. Reporter: We met defense secretary ash Carter on the "Uss Roosevelt." On patrol in the south China sea, the accept center of this new clash, America surveillance shows China on a building spree. One of the biggest back in 2012. Here it is today. The new construction is making other countries nervous, this territory around the spratly islands is claimed by many, including Vietnam and the Philippines. They built hundreds of meters in the past couple of months. Reporter: U.s. Military planes watching from the air and this week going further, president Obama sending a guided missile destroyer within 12 nautical miles of one island. Cruising right by the Roosevelt during our interview. What are we trying to accomplish do you think shoo that are going to stop doing what -- Well, what we're doing is what we have done for decades, that's a reflection of the American military presence in this region, and we're strengthening that with president Obama. Why is that? Because if the American strength here has kept peace in the region which has no nato, no security structure, that's the reason we're out here. Reporter: The U.S. Is also here because more and more asian countries want to keep China in check. Also former enemies like Vietnam. Secretary Carter was there in June. Who would ever thought that Vietnam would want us back here? I remember very well a time when we were at war with Vietnam, now they very much want the American presence and that relationship and that was my purpose. Reporter: Regarding this new dispute, China's president saying this area has been China's territory since ancient times. More aggressive China under president xi? Well, this is widely viewed in the region as an aggressive act. And the United States regards it -- by the way, China is the only country doing this. We challenge all of the president xi, when he came to the United States to visit president Obama, pledged, said he had no intention of militarizing that region. And he needs to be good to his word. For our part, we'll continue to sail, fly, operate wherever international law permits. Reporter: For "This week," bob woodruff, ABC news, on the uss Roosevelt in the south China sea. Thanks to bob for that. Now, we honor our fellow Americans who serve and sacrifice. In the month of October, nine service members were killed supporting operations in Afghanistan and Iraq. That's all for us today. Thanks for sharing part of your Sunday with us. Check out "World news tonight" and I'll see you tomorrow on "Good morning America."
This transcript has been automatically generated and may not be 100% accurate.