A Chinese military aircraft crossed near the nose of a Navy P-3C Orion anti-submarine and surveillance plane Wednesday, flying within about 1,000 feet in an encounter the Pentagon identified as unsafe, but probably unintentional.

The incident occurred late in the morning in international airspace over the South China Sea near Scarborough Shoal, said Navy Capt. Jeff Davis, a Pentagon spokesman. The Chinese plane’s maneuver prompted the Navy aircraft to turn to avoid it.

“Clearly, we have our disagreements with China over militarization of the South China Sea, over their reclamation of the islands and some of their broader strategic objectives, but when it comes to simply the interactions, those are largely professional and safe,” Davis said. “This does seem to be a one-off. It doesn’t seem to indicate that it’s a change in their policy or strategy, and our immediate assessment is this was likely unintentional.”

The incident came one day before President Trump, in a conversation with China’s President Xi Jinping, agreed to honor the one-China policy, after weeks of tension that began when Trump suggested he would only commit to the agreement if China addressed concerns he has about trade and the valuation of China’s currency. The policy rules out independence or U.S. diplomatic recognition for Taiwan, and was first agreed to in 1972 by President Richard Nixon and China’s Mao Zedong.

China, whose expansion in the South China Sea continues to be a friction point with the United States and other nations, had several interactions with U.S. military aircraft in 2014 that raised concerns at the Pentagon. In one case, a Chinese J-11B fighter jet brought the tip of one of its wings within 20 feet of a Navy P-8 Poseidon surveillance plane. But U.S. officials have said those sorts of incidents have dwindled since.

Davis said there was normal radio contact between the Navy plane and the Chinese aircraft, a KJ-200 that is designed to perform airborne early-warning and control, a mission that detects planes, ships and vehicles at long ranges. Asked what the incident says about the Chinese early-warning system, Davis said that is a “very good point,” but did not answer directly.

“Look, these things do happen,” Davis said. “We have a lot of interaction with the Chinese. This is not in and of itself unusual that our planes or our aircraft or our ships encounter each other. Where we get concerned is when we see things that are unsafe or unprofessional, and when we do see those we raise them through our appropriate channels.”

An unnamed Chinese Foreign Ministry official, speaking to the Global Times newspaper, said the incident took place after two Chinese fighters had followed and monitored the U.S. plane “while maintaining a safe distance.” No dangerous action was taken, the Chinese official said.

In December, a Chinese naval ship seized an underwater drone used by the United States to test water conditions in the South China Sea, the Pentagon said. China returned it within a few days, despite Trump, then the president-elect, tweeting: “We should tell China that we don’t want the drone they stole back.- let them keep it!”

Simon Denyer contributed to this report.