WASHINGTON (Reuters) - A top Chinese general toured an American aircraft carrier on Tuesday at the start of a U.S. visit expected to expose tensions over territorial disputes between Beijing and U.S. allies in the South and East China Seas.

General Fang Fenghui, chief of the general staff of the Chinese People's Liberation Army, visited the nuclear-powered Ronald Reagan in San Diego, California, escorted by the head of the U.S. military's Pacific Command, Admiral Samuel Locklear.

Fang was expected to visit the National Defense University in Washington On Wednesday, and meet the top U.S. military officer, General Martin Dempsey, at the Pentagon on Thursday.

Chinese military brass are no strangers to U.S. warships, including aircraft carriers, and PLA navy chief Admiral Wu Shengli visited the carrier Carl Vinson last year.

But Fang's visit is the latest example of efforts by both countries to improve military ties as China ramps up defense spending, investing in sophisticated hardware, including "carrier killer" missiles, which Pentagon officials suspect are aimed at countering U.S. military capabilities.

It is also an opportunity for the two sides to discuss tensions in the South China Sea, which again flared last week when China positioned a giant oil rig in an area also claimed by Vietnam. China also rejects rival claims from U.S. ally the Philippines as well as from Taiwan, Malaysia and Brunei in the resource-rich waters.

"They are going to talk about areas where we agree as well as areas where we have differences," said one U.S. official, speaking on condition of anonymity.

"We disagree with some of their approaches to problem solving in the South China Sea."

In the East China Sea, Beijing is locked in an increasingly bitter dispute with U.S. ally Japan over the ownership of a group of uninhabited islets.

North Korea was also expected to be on the agenda, following renewed threats by Pyongyang to carry out another nuclear test.

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Analysts say efforts by the United States and China to increase military contacts could be helpful in preventing an incident at sea from escalating into conflict.

Those efforts includes Fang's visit, as well as one by U.S. Defense Secretary Chuck Hagel a month ago to China, where he toured China's sole aircraft carrier, the Liaoning.

"We are in the best cycle in decades in terms of military-to-military relations with the PLA, and we should sustain the momentum to make ourselves smarter about China's progress," said Douglas Paal of at the Carnegie Endowment for International Peace, a think tank in Washington.

(Reporting by Phil Stewart, David Brunnstrom and David Alexander; Editing by Mohammad Zargham)