The Pentagon said there had been 180 incidents since autumn 2021 against US military planes and it increased to 300 when the incidents included aerial intercepts near aircraft flown by allies.

Releasing photographs and videos of some recent incidents, The Pentagon said the Chinese flights over the East and South China Sea regions were risky and aggressive in nature, but stopped short of calling them unsafe - a standard military term when interactions are actually dangerous.

However, officials warned the "reckless manoeuvres" by Chinese aircraft - which included "close approaches at high speeds in the air, releasing objects and projectiles like flares, and other dangerous behaviour" - could cause "active accidents" and lead to an inadvertent conflict.

They said the Chinese flights aimed to "intimidate" the US and its allies.

In one instance, a Chinese fighter plane "approached our asset at a speed of hundreds of miles per hour, clearly armed and closing to just 30 feet away", and stayed there for more than 15 minutes, said Ely Ratner, assistant secretary of defence for Indo-Pacific security affairs.

"All of these examples we've released underscore the coercive intent of (China) by engaging in behaviours, particularly in international airspace," he said.

"The bottom line is that in many cases, this type of operational behaviour can cause active and dangerous accidents."

The claims come at a time US-China relations are at their lowest point in years.

Tensions exist over a range of issues including Taiwan, trade, China's human rights record and its military activity in the South China Sea.

The Pentagon has tried for years to posture itself to be ready for a potential conflict with China over Taiwan, even as it now finds itself supporting allies in Ukraine and Israel.

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Admiral John Acquilino, head of US Indo-Pacific Command, told reporters on Tuesday that despite the US sending carrier strike groups and amphibious ships to support Israel and almost 20 months of war in Ukraine, the command has what it needs to deter China.

"I haven't had one piece of equipment or force structure depart," he said, referring to ships, aircraft and military units.

"We have been taking a number of steps to strengthen our commitment to the region, strengthen our deterrence in the region and we will continue to do that."

Intercepts are when a plane from another military moves up close to an aircraft.

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The US warning on Tuesday came as Canada separately accused Beijing's fighter jets of a "reckless" intercept of a Canadian maritime patrol aircraft in international waters off the coast of China.

Chinese planes shadowed and came within five metres of the Lockheed CP-140 Aurora aircraft, which Canadian defence minister Bill Blair described as unacceptable, dangerous and reckless.

The Canadian surveillance plane was on a mission to enforce UN sanctions against North Korea.

Beijing hit back, accusing the plane of "illegally" intruding into the airspace of Chiwei Yu, an island affiliated to China's Diaoyu Islands.