The U.S. says it will continue to maintain a presence in the South China Sea to keep sea lanes open and air space safe.

Admiral Robert Willard, the head of the U.S. Pacific Command who is currently visiting the Philippines, has expressed strong concerns about China’s military assertiveness in the Asia-Pacific region. He said the issue was discussed with officials in Manila on Wednesday.

Willard said that although the U.S. favors no side in disputes over oil- and gas-rich areas in the South China Sea, it will oppose any use of force in regards to the territorial disputes.

China and a number of Southeast Asian countries are currently battling for sovereignty over territories in the area.

Willard’s comments come as the U.S. and China have been mired in disputes over purchases of U.S. weapons by Taiwan, and U.S. naval drills with South Korea.

Reports say that if the bilateral discord continues, it could negatively affect the response to South Korea’s sunken “Cheonan” warship and the North Korean nuclear issue.