Navy Adm. Samuel J. Locklear III, commander of U.S. Pacific Command, briefs the Pentagon press corps, Jan. 23, 2014.

The top U.S. military commander in the Asia-Pacific region acknowledged his concern on Thursday over entrenched tensions between Japan and China, a day after Japan's prime minister evoked comparisons to Britain and Germany before World War One.

Admiral Samuel Locklear, the head of the U.S. military's Pacific Command, said the role of the United States was to keep encouraging restraint, professionalism and "hope there will be diplomatic dialogue and a solution to this."

"I am concerned," Locklear told a Pentagon briefing, after being asked to assess the tensions between Japan and China and the risk of conflict.

"Anytime you have two large powers, two large economic powers, two large military powers, that have a disagreement that they're not talking to each other about, that has no clear diplomatic end state in sight. ... The risk calculation can grow."

Sino-Japanese ties, long plagued by what Beijing sees as Japan's failure to atone for its occupation of parts of China in the 1930s and 1940s, have worsened recently due in part to a territorial dispute in the East China Sea, where China declared an air defence zone late last year.

Ties have also suffered because of Tokyo's mistrust of Beijing's military buildup and Japanese Prime Minister Shinzo Abe's December visit to a shrine that critics say glorifies Japan's wartime past.

Abe said on Wednesday that Japan and China should avoid repeating the past mistakes of Britain and Germany, which fought in World War One despite strong economic ties, according to his main government spokesman in Tokyo.

China and Japan, the world's second- and third-largest economies respectively, have deep business ties and bilateral trade worth nearly $334 billion in 2012, according to Japanese figures.

HOTLINE

The U.S. military's ability to quickly defuse a crisis in the East China Sea is unclear, and Locklear said he did not have a hotline to his counterpart in China's People's Liberation Army.

"I don't have the ability to pick up the phone and talk directly to a PLA, or PLA Navy admiral, or general, at the time of a crisis. And we need to work on that," Locklear said.

He did say that Defence Secretary Chuck Hagel and General Martin Dempsey, the chairman of the Joint Chiefs of Staff, did have capabilities to reach out in a crisis and "we would hope it would work".

U.S. Deputy Secretary of State William Burns concluded a three-day trip to China on Thursday in which he met senior Chinese leaders and "stressed the importance of all sides avoiding unilateral action to assert territorial and maritime claims and for China to work constructively with its neighbours to reduce tensions in the East China Sea and the South China Sea." the U.S. State Department said.

"He reiterated long-standing U.S. interests in all parties managing the situation diplomatically," State Department spokeswoman Marie Harf said in a statement.

The risks of a mishap in the region were highlighted last month when the guided missile cruiser USS Cowpens had to take evasive action to avoid hitting a Chinese warship operating in support of Beijing's first aircraft carrier, the Liaoning.

Locklear said the incident had prompted a U.S. demarche - a formal diplomatic statement of concern - to Beijing.

China believed it issued notification to maritime traffic to steer clear of the Liaoning, Locklear said. But he added that the Cowpens, which was monitoring the carrier, had no such notice.

Locklear has attributed the incident to the Chinese navy's inexperience with deployments in international waters around other warships, one reason the U.S. officials are looking forward to China's participation in the U.S. military's multinational RIMPAC naval exercises near Hawaii this year.

"We have to expect that the U.S. and the Chinese navies are going to interact with each other," Locklear said.

"So this just highlights ... to both the PLA and to the U.S. military that we have to do better at being able to communicate with each other in a way that allows us to not lead to miscalculation."

(Agencies)