Chinese Vice President Xi Jinping on Monday urged China and the United States to deepen mutual trust and expand common ground to improve military cooperation.

Xi made the comment in Beijing after a meeting with U.S. Admiral Mike Mullen, chairman of the U.S. Joint Chiefs of Staff. He hailed what is widely seen as improving Sino-U.S. ties, saying they represent one of the world's most important bilateral relationships.

Earlier in the day, China's military chief, General Chen Bingde, criticized the timing of U.S. naval exercises in the South China Sea and surveillance flights off its shores.

Speaking alongside Mullen, Chen said the maneuvers with the Philippines and Vietnam were “extremely inappropriate” at a time when China is embroiled in tense territorial disputes with both countries.

Mullen, who is in China on a four-day visit, responded that the United States has been staging drills with its friends and allies in the region for decades and will continue to do so. He said the United States will also continue the surveillance flights, which are within “international norms.”

General Chen also said the U.S. is spending too much on its military and is putting too much pressure on American taxpayers in the wake of the global economic crisis.

Chen told the official Xinhua news agency that apart from the South China Sea disputes, he and Mullen had discussed cyber security, China's military development and the attitude of some U.S. politicians toward China.

Mullen's visit to China is the first by a U.S. military chief of staff since 2007. 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.