A high-ranking U.S. Navy officer acknowledged Monday he participated in a routine surveillance flyover of the disputed waters of the South China Sea Saturday. Chinese defense officials have responded by saying the move has contributed to the continuing strain on bilateral relations between Washington and Beijing.

Adm. Scott Swift, the commander of the U.S. Pacific Fleet, confirmed at a press conference in Seoul, South Korea, that he had been aboard a seven-hour Boeing P-8 surveillance flight to oversee the military’s new operational capabilities, Reuters reported.

“We have forces deployed throughout the region to demonstrate the United States commitment to freedom of navigation,” Swift said. It was a routine flight, and the fleet commander did not mention whether Chinese forces responded to it. However, he said communication between the U.S. and China at sea were “positive and structured.”

However, China appeared to have a different take on the two countries’ relations at sea in the wake of the surveillance flight Saturday.

“For a long time, U.S. military ships and aircraft have carried out frequent, widespread, close-in surveillance of China, seriously harming bilateral mutual trust and China’s security interests, which could easily cause an accident at sea or in the air,” China’s Defense Ministry said in a statement made to Reuters.

However, the U.S. indicated China also has contributed to any strain on Sino-U.S. relations over the issues centered on the South China Sea. “There are forces of instability at play in the region, and that’s generating uncertainty,” Swift said at the press conference.

China has claimed at least 80 percent of the South China Sea, where it has pursued massive land-reclamation projects in the disputed waters. Objecting to these projects are several Southeast Asian countries, such as Malaysia, the Philippines and Vietnam, all of which have overlapping claims. Both as a military ally of the Philippines and in line with the Obama administration’s so-called pivot to Asia, the U.S. has been keeping tabs on China’s moves in the maritime region, as evidenced by the surveillance flyover this weekend.