Chinese dredging vessels are purportedly seen in the waters around Mischief Reef in the disputed Spratly Islands in the South China Sea in this still image from video taken by a P-8A Poseidon surveillance aircraft provided by the United States Navy, May 21, 2015. Reuters

A U.S. Navy plane came within 1,000 feet of a Chinese military aircraft over the South China Sea in an accident that could fuel tensions between the world leaders over the disputed territory. The aircraft nearly collided while flying over the Scarborough Shoal, between the Philippines and the Chinese mainland, Reuters reported Thursday.

Chinese and U.S. aircraft also flew close to each other twice in 2016 without incident. The U.S. plane was a P-3 Orion aircraft and the Chinese plane was a People's Liberation Army Air Force KJ-200.

A Navy spokesman said the near accident was "unsafe." The Navy plane was forced to change course to avoid a collision.

"The U.S. Navy P-3C was on a routine mission operating in accordance with international law," Maj. Rob Shuford told CNN. "The Department of Defense and US Pacific Command are always concerned about unsafe interactions with Chinese military forces. We will address the issue in appropriate diplomatic and military channels."

China claims it controls the South China Sea, which includes islands more than 800 miles from the Chinese mainland, and has built artificial islands in the area, including what appear to be military bases. The Chinese Coast Guard regularly patrols the area, but the Philippines, Malaysia, Brunei and Vietnam also claim to have a stake in the region and the U.S. has urged China to allow for open travel in the South China Sea.

President Donald Trump and Secretary of State Rex Tillerson have vowed to take a tougher stance against China, including over its rule over the South China Sea.

China has defended its construction in the region. "The necessary military facilities are mainly for self defense. When someone is flexing muscles at your doorstep, wouldn't you ­prepare a slingshot?" a statement from the government in December said.