The United States has sent its largest military force to Vietnam since the end of the war in 1975. The aircraft carrier Carl Vinson and two other ships have dropped anchor off the coast of Da Nang, where US troops first stormed ashore to start the war.

What the US Navy is describing as a routine port stop is being seen as a direct signal to China.

Al Jazeera's Wayne Hay reports from Da Nang.

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