Speaking in Washington, Kawano said there had been "talk" of Japan conducting such patrols in the South China Sea, including anti-submarine activities.
"But our position on this is that we consider this as a potential future issue to be considered depending on how things pan out,” he told the Center for Strategic and International Studies think tank.
Kawano earlier met with his U.S. counterpart, General Martin Dempsey, chairman of the Joint Chiefs of Staff, and discussed implementation of updated bilateral defense guidelines agreed this year, a joint statement said.
Tensions have been rising in the South China Sea, home to important international shipping lanes, due to overlapping territorial claims and rapid building of artificial islands by China that has been criticized by Tokyo and Washington.
China claims most of the South China Sea and has territorial rivalries there with several Southeast Asian states. It also has competing claims with Japan in the East China Sea, further to the north.
