In a sign of the deepening ties between the two nations' armed forces, Guo Boxiong, vice-chairman of China's Central Military Commission (CMC), is expected to arrive in the United States today.

Guo, whose visit comes at the invitation of Defence Secretary Donald Rumsfeld, is the highest-ranking officer to visit the US since 2001.

He ranks second to Chairman Hu Jintao in the 11-member CMC, China's top military authority.

Guo's visit comes as China-US military relations are "at their best since 2001," said Qian Lihua, deputy director of the Foreign Affairs Office of the Defence Ministry.

Qian said Guo's US visit is "the most important Chinese military exchange with another country this year."

During his stay in Washington, Guo is scheduled to hold talks with Rumsfeld on a wide range of issues, including international and regional security, and China-US military ties.

He will also meet with other members of the Bush administration.

In addition, the week-long visit will take Guo to US military bases and institutions.

Analysts say co-operative agreement on specific fields might come out of the visit.

"Guo's visit will help promote trust and expand co-operation in security fields," said Yang Yi, director of the Institute for Strategic Studies at the National Defence University of China.

Among Guo's entourage are the Political Commissar of Chinese People's Liberation Army (PLA) Nanjing Military Area Command Lei Mingqiu, Assistant to the PLA Chief of the General Staff Zhang Qinsheng, Deputy Commander of PLA Navy Zhao Xingfa, Deputy Commander of PLA Air Force Liu Chengjun, and Chief of Staff of PLA Second Artillery Force Yu Jixun.

The visit is the latest in the growing number of high-level visits between Chinese and US armed forces over the past few years.

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.

Editor: Yan