Defense Secretary Ash Carter lashed out at China Wed. for building artificial islands in the South China Sea that could include military air strips.
Carter said the U.S. will continue to fly over the islands, no matter what Beijing says. This is just part of a massive Chinese military buildup.
China said its plan to beef up its naval power will prevent further "meddling" by other countries in the South China Sea.
The new plans could include military operations in the open ocean, not just defending the country's coast line.
It comes at a time of growing tension between China and the United States. Satellite images show China dredging and expanding eight reefs among the Spratly Islands -- and claiming it as new territory.
The U.S. says these artificial islands are a land grab, ultimately to be home to military airstrips and radar installations. Yang Yujin, a spokesman for China's defense ministry brushed off criticism.
"There are all kinds of constructions all over China every day," he said. The island construction is "no different."
The South China Sea is one of the world's busiest shipping lanes. China lays claim to the Spratly Islands, but so do many of its neighbors.
The United States sees it as international waters, and last week the dispute escalated when the U.S. flew a surveillance plane over China's newly constructed islands.
The Chinese foreign ministry defended its claims.
"It's certain countries out of self-interest that are hyping this issue and smearing China's image," said spokesman Hua Chunying.
China's more aggressive military stance is expected to be a topic this weekend at a security conference in Singapore attended by both Chinese military officials and the United States Secretary of Defense.