The Trump administration has raised concerns with China after two Chinese fighter jets intercepted a US military aircraft in a manner the American crew viewed as dangerous.
One person familiar with the incident said one of the Chinese fighters flew upside down as it intercepted a Boeing WC-135 — called the “sniffer” because its mission is to collect air particles to detect nuclear explosions — which was flying over the East China Sea.
US Pacific Command, which oversees American military operations in Asia, said two Chinese Sukhoi jets flew unprofessional manoeuvres at an unsafe distance and speed. The Pentagon has deployed the sniffer to the region because of concerns that North Korea could conduct a sixth nuclear test at some point.
The incident marks the first known complaint the Pentagon has lodged with China since Donald Trump became president. It comes as he urges China to increase pressure on North Korea to abandon its nuclear and missile programmes. On Monday Pyongyang claimed to have developed a long-range missile that could carry a nuclear warhead.
Some North Korea experts had expected Pyongyang to conduct a nuclear test last month. The Trump administration views North Korea as its most serious foreign policy challenge as Pyongyang moves closer to being able to hit the US with a nuclear-armed missile.
“These incidents are very rare,” said Paul Haenle, director of the Carnegie-Tsinghua Center in Beijing. “None were reported in 2015 and only two in 2016. “In February, there was an ‘unsafe encounter’ — not an intercept — between a US Navy P-3 Orion aircraft and a Chinese surveillance aircraft near Scarborough Shoal.”
Mr Haenle, who served as the former top White House China adviser to George W Bush and Barack Obama, said the US and China in 2015 had established a military hotline and agreed on rules of behaviour to govern air-to-air encounters that were aimed at preventing dangerous interceptions.
“It’s possible that Chinese pilots have not improved, but I think more likely that they are signalling their ongoing displeasure with US close surveillance and reconnaissance activity,” he added.
The Chinese ministries of defence and foreign affairs made no immediate comment.
“This interception signals that China is willing to defend its claim over the East China Sea air space,” said Shi Yinghong, director of the Center for American Studies at Renmin University.
“The Chinese government is obviously more assertive and stronger than Trump’s administration right now,” Mr Shi added. “Trump’s only achievement is the improvement of Sino-US relations, so China knows that Trump wouldn’t dare to ruin these relations. China has the self-confidence to guard its sovereignty now.”
In 2013 China unilaterally established an air defence zone over most of the East China Sea, claiming the right to prevent foreign aircraft from entering. The US has not recognised China’s claim.
Relations between the US and Chinese militaries appeared to improve in recent months, particularly as the US Navy has not conducted any of the “freedom of navigation” operations (Fonops) in the South China Sea that anger the Chinese government.
While some experts have speculated that the US had pulled back in the South China Sea to avoid antagonising China as Washington seeks co-operation on North Korea, one US official said the focus on the lack of operations in the South China was misplaced.
“We are very focused on a couple of big strategic issues in north-east Asia right now,” said the official. “We have dual carrier operations, bombers, joint exercises with Japanese and South Korea. We have a lot going on out there. The focus on Fonops is frankly just misplaced.”
Lieutenant Colonel Lori Hodge, a US Air Force spokesperson, said the crew on the Boeing WC-135 viewed the way the Chinese fighters intercepted them as “unprofessional” because of the “manoeuvres by the Chinese pilot, as well as the speeds and proximity of both aircraft”.
She said the US was addressing the issue through diplomatic channels and a mechanism used to tackle issues between the two militaries.
“This will allow us to continue building confidence with our Chinese counterparts on expected manoeuvring to avoid mishaps,” said Col Hodge.
Additional reporting by Yingzhi Yang
Follow Demetri Sevastopulo on Twitter: @dimi