US and Chinese military planes flew dangerously close to one other this week near a disputed shoal in the South China Sea, in an incident that a Navy official described as unsafe but inadvertent.

The official, speaking on condition of anonymity to Reuters, said the planes passed within 1,000 feet of each other as they flew near the Scarborough Shoal, where China and the Philippines have scuffled in recent years over administration and fishing rights.

Such incidents between US and Chinese aircraft are rare, the source added. But it returns attention to the long list of close encounters and mini-provocations involving China, the United States, and US allies in the region, at a time when relations between the two behemoths have become less amicable and predictable than in recent years.

Ministries from both China and the US acknowledged the close fly-by in official statements. "On Feb. 8, an interaction characterized by U.S. Pacific Command as 'unsafe' occurred in international air space above the South China Sea, between a Chinese KJ-200 aircraft and a U.S. Navy P-3C aircraft," US Pacific Command told Reuters.

"The Department of Defense and U.S. Pacific Command are always concerned about unsafe interactions with Chinese military forces," it added.

"We will address the issue in appropriate diplomatic and military channels."

China’s defense ministry defended the Chinese pilot’s conduct in an interview with state media, saying the pilot had taken "legal and professional measures."

"We hope the U.S. side keeps in mind the present condition of relations between the two countries and militaries, adopts practical measures, and eliminates the origin of air and sea mishaps between the two countries," an unnamed defense official told the Global Times.

The Scarborough Shoal is in many ways the center of South China Sea tensions. The shoal was US territory during the Philippines’s period as an American colony and passed over into Philippine control upon independence in 1946. The US maintained a military base on a nearby island until 1991 and carried out joint exercises on the shoal with the Philippines.

In a 2012 standoff with the Philippine Navy, China established effective control over the shoal. It has since allowed Filipino fisherman to work the waters around it. But China’s decision to ignore a United Nations tribunal’s ruling on its South China Sea claims – combined with its building of artificial islands and military installations in the nearby Spratly archipelago – has led many to suspect that it ultimately has its eye on the shoal as a military outpost.

"Because of its position, another military outpost at Scarborough Shoal is seen as the last major physical step required to secure control of the sea," notes the Agence France-Press.

"An outpost at the shoal would also put Chinese fighter jets and missiles within easy striking distance of US forces stationed in the Philippines."

"The shoal also commands the northeast exit of the sea, so a Chinese military outpost there could stop other countries' navies from using the vital stretch of waters."

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News of the close fly-by comes as President Trump seems to have changed tack on the “one China” policy, telling Chinese leader Xi Jinping that the US would honor it during a lengthy phone call on Thursday night. Mr. Trump had shocked Beijing by accepting a congratulatory phone call from Taiwan’s president and previously saying the US had no obligation to abide by the policy.

This report contains material from Reuters.