The Liaoning, the only operational aircraft carrier in the Chinese fleet, arrived in the southern port amid recent tensions with U.S. forces in the South China Sea.
Satellite photos show what analysts say is an array of anti-aircraft guns, cruise missile defenses, in nearly identical emplacements on islands created around large reefs.
China isn't disputing the claim. Its foreign minister, Wang Yi, says the country has lawfully deployed "limited, necessary defense facilities" on the island in the South China Sea.
Hanoi and Washington hope to strengthen economic and defense ties, especially in the wake of Beijing's construction on a disputed reef in the South China Sea.
The concern follows reports that China has placed mobile artillery on a reef in the disputed Spratly Islands chain, where Beijing is in the midst of unilateral land reclamation and construction.
The scale of China's construction in the South China Sea's Spratly Islands is clear in new satellite images released by the Asia Maritime Transparency Initiative, whose director speaks with NPR.
Satellite imagery of a coral atoll in the South China Sea shows the reef is growing. A U.S. military official likens Beijing's land reclamation to building a "great wall of sand."
The meeting between foreign ministers on both sides is the first such dialogue in four years after relations were frozen by Beijing in 2011 over a disputed island chain in the East China Sea.