The top military commanders from the United States and China say they held “candid” talks Monday about territorial disputes in the South China Sea and other contentious issues.

The official Xinhua news agency quoted Chinese armed forces chief Chen Bingde saying the two also discussed cyber security, China's military development and the attitude of some U.S. politicians toward China.

Admiral Mike Mullen is in Beijing on a four-day visit, the first by a U.S. military chief of staff since 2007. Xinhua quoted Chen saying the two found “a lot of common ground” but had “different opinions on certain issues.”

Mullen said after his arrival in Beijing Sunday that he is worried about China's disputes with the Philippines and Vietnam over competing territorial claims in the resource-rich South China Sea. China says the United States should stay out of the disputes.

Washington recently reaffirmed its commitment to a mutual defense treaty with the Philippines.

The United States has also declared a national interest in maintaining free navigation through the South China Sea, which carries vital sea traffic between Northeast Asia, and Europe and the Middle East.

Speaking Sunday at Beijing's prestigious Renmin University, Mullen said the United States is, and will remain, a Pacific power. But he said the regional and global challenges facing the U.S. and China are too large and too vital to be blocked by misunderstandings.

Mullen also called for greater openness from China's growing military. He said that “with greater military power must come greater responsibility, greater cooperation and just as important, greater transparency.”

During his visit, Admiral Mullen is due to visit Chinese military bases outside Beijing. His meetings are also expected to deal with stalled nuclear disarmament talks with North Korea, U.S. arms sales to Taiwan and confidence building measures between China and the United States.

China, the Philippines, Vietnam, Malaysia, Brunei and Taiwan all claim territory in the South China Sea, with most of those claims centered on the potentially energy rich Paracel and Spratly island chains. China's claim is the largest and it has issued sharp warnings in recent weeks, including threats of military action, to enforce its claims.