U.S. officials said it's not the first time China has placed J-11 and J-7 fighter jets on Woody Island, part of the Paracel island chain in the hotly disputed region, after expanding the runway there in 2014.
"The specifics of a recent deployment of fighter aircraft to Woody Island would be less an issue than the signal it sends of how far out of step China's actions are with the aspirations of the region," a Pentagon spokesman said in a statement.
The placement of missiles on the island, which appear to be permanently placed in concrete, is of greater concern, according to the officials.
China controls the Paracel chain, but Taiwan and Vietnam also claim it; Brunei, Malaysia and the Philippines are also embroiled in disputes with China over regional islands and their surrounding waters. Read more on edition.cnn.