The chairman of the U.S. Joint Chiefs of Staff urged the Chinese leadership to rein in North Korea to prevent further unprovoked attacks on South Korea.

U.S. Navy Adm. Michael Mullen, on the first visit of a chairman of the Joint Chiefs of Staff to China in four years, told journalists in Beijing that historically North Korea is likely to launch another attack against South Korea.

But China could help stabilize the area by exerting its influence with Pyongyang and advising against such acts.

"The provocations I think now are potentially more dangerous than they have been in the past," said Mullen at the start of a 4-day visit.

"All of us are focused on a stable outcome here of what is increasingly a difficult challenge with respect to the leadership in North Korea and what it might do."

At issue is a change in leadership at some time in the near future when Kim Jong Il likely hands over to his youngest son, Kim Jong Un. The son remains a largely unknown figure and possibly an insecure leader who may try to garner credibility with North Korea's military by launching attacks.

An unprovoked attack in which South Korea restrains from severe retaliation -- as happened in November -- could raise the profile of Kim Jong Un and boost his credibility with North Korea's generals. The Chinese, said Mullen, could dissuade a new North Korean leadership from such attacks.

Relations between the two Koreas rang alarm bells in Washington and Beijing in November when North Korea unexpectedly shelled the South Korean island of Yeonpyeong in the Yellow Sea and several miles from the North's mainland.

The daylight attack, in which North Korea fired around 170 shells, damaged dozens of houses and several military buildings. It also killed two South Korean marines and two civilians and injured at least 20 other people. South Korean forces returned fire but there were no known causalities to North Koreans.

Relations already were low after the sinking in March last year of the South Korean navy's 1,200-ton patrol ship Cheonan in which 46 sailors died. Seoul blames North Korea, which continues to deny it was involved.

"The Chinese leadership, they have a strong relationship with the leadership in Pyongyang and they exercise that routinely ... continuing to do that as they have done in the past is really important," Mullen said.

Specifically, the stalled six-party talks among China, which hosts them, the two Koreas, Japan, the United States and Russia, could be restarted. The talks, which cover North Korea's denuclearization, were shelved in 2009 when Pyongyang pulled out to protest U.N. sanctions over its nuclear tests.

However, South Korea maintains there can be no talks unless the North demonstrates its denuclearization commitment and takes responsibility for torpedoing of the Cheonan and shelling Yeonpyeong Island.

Mullen's visit is the start of a thaw in U.S.-China military relations, welcomed by both countries. China put a stop to contacts over U.S. military sales to Taiwan, which Beijing considers an integral part of China.

The visit also is a reciprocation of a visit to the United States in May by his Chinese counterpart Gen. Chen Bingde.

Their discussions and meetings in Beijing come at a time of increased tensions not just on the Korean Peninsula but in the South China Sea. Several countries, including China, the Philippines and Vietnam, have territorial claims to islands and reefs that are the source of naval confrontations.

At stake is ownership of potentially huge oil and gas reserves on the seabed surrounding the islands.

Mullen said the United States will stand by its allies in the region and continue to hold joint naval exercises as has been the case with the Philippines and Viet Nam.

China had expressed concern over a recent 11-day joint naval exercise by the U.S. Navy and that of the Philippines.

During a speech to students at Renmin University of China in Beijing, Mullen warned that misunderstanding over territorial sovereignty and resource research activities could lead to "an outbreak that no-one anticipated."

He said the United States is committed to remaining a power in the area. "We are, and will remain, a Pacific power, just as China is a Pacific power."

Later, after a closed door meeting, Chen said he and Mullen discussed, apart from the South China Sea, the attitude of some U.S. politicians toward China, cybersecurity and China's military development.

"It's fair to say that we found a lot of common ground while we do have different opinions on certain issues," Chen said.

Chen urged the two sides to implement the consensus reached by their heads of state to push forward the development of bilateral military relations, the China Daily newspaper reported.