Japan, a major ally of the United States, has been engaged in a diplomatic dispute with China over control of the South China Sea. In then-Secretary of State Hillary Clinton's inaugural tour of East Asia, she reassured Japanese officials of Japan's centrality in the network of American alliances. In response to the 2011 Tōhoku earthquake and tsunami, the United States initiated Operation Tomodachi to support Japan in disaster relief following the 2011 Tōhoku earthquake and tsunami earning gratitude from Japan's minister of defense, Toshimi Kitazawa who, while visiting the "Ronald Reagan", thanked its crew for its assistance as part of Operation Tomodachi saying, "I have never been more encouraged by and proud of the fact that the United States is our ally."