Marine Corps Gen Joseph Dunford, the chairman of the Joint Chiefs of Staff, made the remarks at the opening of a meeting with Fang Fenghui, chief of the People's Liberation Army's joint staff department.
US officials say Dunford's visit aims to create a mechanism for improving communication between the sides, especially on sensitive issues such as North Korea.
Dunford is visiting South Korea, Japan and China after a week in which President Donald Trump said he was ready to unleash "fire and fury" if North Korea continued to threaten the US.
To that end, China has arranged a series of important meetings and visits to help Dunford "know more about our military, (boost) our cooperation and build up our friendship," Fang said.
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Dunford responded that the US considered the meetings important to making progress on areas of disagreement, without citing any specific examples.
"I think here, we have to be honest - we have many, many difficult issues where we don't necessarily share the same perspective," Dunford said.
While the sides agreed to establish a hotline between the Pentagon and China's defense ministry several years ago, that mechanism has never gone into operation. US officials say they've attempted to use it, but that the Chinese side has never answered their requests.