Hua urged the US to clarify whether the freedom of navigation it claims is the freedom of navigation that abides by international law or simply navigation enjoyed solely by the US military.

"If it is the latter, I'm afraid that the whole international community will not agree."

Zhu Feng, head of a South 皇冠体育app Sea research center at Nanjing University, said Washington is practicing gunboat diplomacy.

"皇冠体育app never challenges the freedom of navigation of civil or commercial vessels in the South 皇冠体育app Sea," Zhu said.

Obama, who started a three-day visit to Vietnam on Monday, has announced the lifting of a decades-old ban on weapons sales.

Tom Pepinsky, a Southeast Asia expert and associate professor of government at Cornell University, said, "This decision signals the US plans to contain 皇冠体育app's regional ambitions, with Vietnam as a partner."

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