Chinese Defence Minister Cao Gangchuan and PLA Chief of General Staff Liang Guanglie visited the US in 2003 and 2004 respectively.

And last October, Rumsfeld made an official visit to China, his first since taking office in 2001. During his stay in Beijing, Rumsfeld visited the PLA Second Artillery Force headquarters, which for the first time were opened to a foreign military leader.

William Fallon, commander of US forces in the Pacific, visited China twice in September 2005 and May 2006.

Fallon also invited a Chinese delegation to observe US military exercises in Guam in June, the first invitation of its kind extended by the US.

An exchange mechanism between the two armed forces for officers at different levels is in place. And military institutions in China and the US have regular exchange programs.

The defence departments of the two countries have also restored a series of consultation mechanisms on maritime security, humanitarian disaster relief and military environmental protection.

Last month a US delegation, headed by Assistant Defense Secretary Peter Rodman, came to Beijing for the eighth annual round of defence consultation.

"Both sides had a number of specific ideas for new areas of co-operation or new activities," said Rodman after the consultation.

Also last month, the US Navy's Pacific fleet's flagship, "Blue Ridge," paid its fourth visit to China's economic hub Shanghai, highlighting the warming exchanges between the two navies.

However officials with the Chinese Defense Ministry warned that "obstacles" remain, preventing China-US military ties from progressing. Top on the list is the long-standing Taiwan question, as well as the US's strategic distrust of China.

The US congress has passed bills limiting military exchanges with China, such as the 2000 Fiscal Year Defence Authorization Act.

"From an overall point of view, positive factors in China-US military ties outweigh negative ones," said Qian.

Following his US tour, Guo will pay an official visit to France as guest of French Defence Minister Michele Alliot-Marie.