Secretary of Defense Leon Panetta announced this weekend that up to 60 percent of American warships will soon be deployed in East Asia. To underscore the United States’ commitment to the region, he visited the deepwater port of Cam Ranh Bay in Vietnam on Sunday.

Panetta was the most senior American official to visit Cam Ranh Bay since the end of the Vietnam War when it served as a key logistic hub for South Vietnamese and United States forces.

As the United States are “rebalancing” their military to the Pacific, “it will be particularly important to be able to work with partners like Vietnam to be able to use harbors like this as we move our ships from our ports on the West Coast toward our stations here in the Pacific,” said Panetta.

Relations between Vietnam and the United States have markedly improved in recent years despite the troubled history. In large part, that’s because Vietnam worries about the rise of neighboring China.

Border disputes and regional rivalry continue to frustrate Sino-Vietnamese relations even as the latter country joined in a free-trade agreement with other Southeast Asian states and China in January of last year.

Chinese revisionist maritime border claims in the South China Sea in particular are forcing other countries in the area to seek American protection.

Panetta’s visit to Vietnam was part of a week long trip in Asia to explain the Obama Administration’s “pivot” to the region. Other nations, too, are quite receptive of the increased American military presence.

When Panetta attended a security conference in Singapore, the island state announced that it had agreed to forward deploy up to four American combat ships in its harbor.

General Martin Dempsey, the American military chief, traveled to the Philippines on Sunday to talk about rotational deployment of US Navy ships there. Vietnam and the United States held naval exercises last month.

China, for its part, has tried hard not to look concerned. “We should not treat this as a disaster,” said Lieutenant General Ren Haiquan, China’s top representative at the Shangri-La Dialogue security forum in Singapore. In comments reported by Hong Kong’s Phoenix Television, he added, “I believe that this is the United States’ response to its own national interests, its fiscal difficulties and global security developments.”

In Beijing, his masters cannot but regard this development warily though.