The U.S. holds drills in South China Sea amid tensions with China

The U.S. Navy and Marine Corps are holding joint exercises in the South China Sea at a time of heightened tensions with Beijing over the shooting down of a suspected Chinese spy balloon.

The 7th Fleet based in Japan said Sunday that the USS Nimitz aircraft carrier strike group and the 13th Marine Expeditionary Unit have been conducting “integrated expeditionary strike force operations” in the South China Sea.

It said exercises involving ships, ground forces and aircraft took place Saturday but gave no details on when the began or whether they had ended.

China claims virtually the entire South China Sea and strongly objects to military activity by other nations in the contested waterway through which $5 trillion in goods are shipped every year.

The U.S. takes no official position on sovereignty in the South China Sea, but maintains that freedom of navigation and overflight must be preserved. Several times a year, it sends ships sailing past fortified Chinese outposts in the Spratly Islands, prompting furious protests from Beijing.

The U.S. has also been strengthening its defense alliance with the Philippines, which has faced encroachment on islands and fisheries by the Chinese coast guard and nominally civilian but government-backed fleets.

The U.S. military exercises were planned in advance. They come as already tense relations between Washington and Beijing have been exacerbated by a diplomatic row sparked by the balloon, which was shot down last weekend in U.S. airspace off the coast of South Carolina.

The U.S. said the unmanned balloon was equipped to detect and collect intelligence signals, but Beijing insists it was a weather research airship that had accidently blown off course.

The incident prompted Secretary of State Antony Blinken to abruptly cancel a high-stakes trip to Beijing last weekend aimed at easing tensions.