U.S. Secretary of Defense Chuck Hagel arrived in China's eastern port city of Qingdao on Monday, beginning his three-day visit to China for discussions on global and regional security issues, including North Korea's nuclear programs. China is Hagel's third stop on his 10-day trip across the Asia-Pacific and his first visit to Beijing as the U.S. defense chief. The trip comes at a time when regional tensions have been growing amid the North's threat of a fresh nuclear test and growing rivalry between Beijing and Tokyo. In Qingdao, Hagel toured China's first aircraft carrier, the Liaoning, which was commissioned in 2012 as a symbol of China's growing military might, according to U.S. officials.