“Lack of transparency”. That was the oblique buzz phrase on the lips of a top US naval officer on Tuesday when pressed on whether China’s largest defence spending increase in three years was of concern.

Accompanying the aircraft carrier USS Carl Vinson’s highly symbolic visit to Vietnam, Vice Admiral Phillip Sawyer, commander of the Asia-based Seventh Fleet, used the term repeatedly to respond to questions about China, including Monday’s revelation that Beijing was boosting defence spending by 8.1 per cent.

“I really can’t speak to the numbers that are published on somebody else’s defence budget. What I can speak to is … about transparency,” the three star admiral said in a telephone interview with regional journalists.

“Lack of transparency causes angst and that is certainly here in the region, and that is potentially disruptive to security and stability and the free flow of commerce and trade,” Sawyer said.

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His comments came as Chinese state media on Tuesday forcefully defended the country’s increased defence spending. Analysts from regional countries including Japan voiced concern about the increase after the release of the annual budget report during the “Two Sessions” parliamentary session.

“China’s defence budget has become a lightning rod for those keen to claim there is a threat from China, for whatever reason,” the English language China Daily said in an editorial that was republished on the Ministry of Defence’s website.

“But although the 2018 defence budget will be 1.11 trillion yuan (US$175 billion), the reality of the matter is the increase, though up from last year’s 7 per cent, is still relatively low compared with many countries in the world,” the newspaper said.

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It added: “As to accusations of China’s rising assertiveness in the East and South China seas, that is a denial of the truth, as China is merely trying to stand up for itself and its rights.”

Sawyer, asked about the Chinese military’s activities in the disputed South China Sea, repeated his mantra that “lack of transparency” was the biggest sticking point.

Rear Admiral John Fuller, the commander of the battlegroup accompanying the USS Carl Vinson, meanwhile said the Nimitz-class nuclear-powered aircraft carrier was continuing operations in the area in accordance with international law.

It was the first time since the end of the Vietnam war that an American aircraft carrier had berthed in the Communist-ruled Southeast Asian country.

While smaller US warships have visited Vietnam in recent years, the 5,500 sailors of the Carrier Strike Group 1 represent the biggest American military contingent in the country since the end of hostilities in 1975.

The port of call, Da Nang, was the site where American combat troops first landed during the bloody, decades-long war.

“We are continuing to show our presence to reassure our friends, allies and partners that the United States is there and we are trying to make sure we support international laws, rules and norms,” Fuller said. “By us being there and by maintaining the free lanes of communications there, we are actually helping to develop prosperity in the region,” he added.

Beijing has previously voiced opposition to the battlegroup’s patrols in the disputed waters, claiming they are “damaging the sovereignty and security of littoral countries under the flag of freedom of navigation and overflight”.

Asked if there had been an official reaction from China to the aircraft carrier’s latest visit to Vietnam, Sawyer said he was unaware of any diplomatic, political or military level contact from Beijing.

Reuters on Monday reported Vietnamese diplomats had been “working for months to ease the concerns of their giant Chinese neighbour” over the visit and the prospect of broader Washington-Hanoi ties.

Zhang Mingliang, an expert in Southeast Asian affairs at Jinan University, said the US hoped to contain China with the help of Vietnam.

“The US hopes that through strengthening military cooperation with Vietnam, Vietnam will be able to adopt a firmer stance against China on the South China Sea issues,” said Zhang, “But it will not be able to change the status quo of China’s control in the South China Sea.”

But Xu Liping, a professor at the Chinese Academy of Social Sciences’ Institute of Asian-Pacific Studies, said the port call was largely “symbolic”.

“The ranking of the Vietnamese officials who hosted the visit was not that high in order not to provoke China,” he said, “The activities they are engaged in are also mainly sports and cultural events instead of activities with clear military purpose.”

While bilateral ties have largely remained cordial, Vietnam is isolated in standing its ground and publicly chastising China over its claim of sovereignty over nearly all of the South China Sea.

Other erstwhile vocal claimants of the disputed waters from Southeast Asia – Malaysia, Brunei, and the Philippines – have watered down their resistance as they seek to tap Beijing’s economic largesse.

With additional reporting by Catherine Wong