"The United States is and will continue to play a critical role in that part of the world in ensuring stability in the Asia-Pacific. A rebalance to the Asia-Pacific is emblematic of that," Pentagon Press Secretary Peter Cook told reporters at a news conference.
He, however could not confirm flights to artificial islands in the South China Sea.
China recently landed a plane on an artificial island it has built in a contested part of the strategic South China Sea, prompting Vietnam to accuse Beijing of "serious infringement" of its sovereignty.
Cook said the Defence Secretary's own visits to Asia recently was an indication of how US feel that part of the world is, and the role that the US military has played in preserving that kind of stability and security, the prosperousness of that part of the world.
"A key reason for that has been the presence of the US military in that part of the world. We are going to continue to play that role and try and do everything we can to maintain that security and stability in the South China Sea and beyond," he said.