The United States has lodged a diplomatic protest after a Chinese fighter jet flew dangerously close to a Navy plane in international airspace, performing aerial manoeuvres just metres away.

The Pentagon said the "very dangerous" incident happened 200 kilometres east of China's Hainan Island on Tuesday near a Chinese submarine base.

Pentagon press secretary Rear Admiral John Kirby said the Chinese fighter jet made several passes at the P-8 Poseidon anti-submarine and reconnaissance plane.

He said the warplane flew underneath the American plane, at the P-8's nose and then in parallel with the wingtips, less than nine metres apart.

"We have registered our strong concerns to the Chinese about the unsafe and unprofessional intercept, which posed a risk to the safety and the wellbeing of the air crew, and was inconsistent with customary international law," Rear Admiral Kirby said.

"The Chinese jet also passed the nose of the P-8 at 90 degrees with its belly toward the P-8 Poseidon, we believe to make a point of showing its weapons load.

"This kind of behaviour not only is unprofessional, it's unsafe.

"And it is certainly not in keeping with the kind of military-to-military ... relations that we'd like to have with China."

He said the move undermined efforts to bolster US relations with China's military.

Deputy White House national security adviser Ben Rhodes said the move was a "deeply concerning provocation".

"We have communicated directly to the Chinese government our objection to this type of action," Mr Rhodes said.

The skies over Hainan Island were the scene of a major international incident in April 2001, when a Chinese fighter jet collided with a US Navy EP-3 spy plane.

The collision left one Chinese pilot dead and forced the American plane to make an emergency landing on Hainan.

Chinese authorities detained the American crew of 24 for 11 days until Washington apologised for the incident, which soured US-Chinese relations in the early days of president George W. Bush's first administration.

AFP/Reuters