The plane was in the area to measure radiation levels
A pair of Chinese planes swooped on the US get flying over the East China Sea.
The American pilot claimed one of the Chinese aircraft flew upside down directly above it.
The US Air Force has criticised its counterpart after the provocative move against the ‘nuclear sniffer’ plane, which in the past has been used to gather information on possible tests by North Korea.
The plane was in the area to measure radiation levels, and was complying with international law, according to Air Force spokesperson Lieutenant Colonel Lori Hodge.
Coming within 150ft of the aircraft as they intercepted it on Wednesday, Lieutenant Colonel Hodge branded the action “unprofessional”.
She said: “While we are still investigating the incident, initial reports from the US air crew characterised the intercept as unprofessional.
“The issue is being addressed with China through appropriate diplomatic and military channels.”
A US Navy spy plane and a Chinese military aircraft came within 1,000 ft of each other
The incident is the latest in a string of defiant actions from both sides, inflaming the already fragile relations between the two superpowers.
And it is the second physical stand-off this year, following a US Navy spy plane and a Chinese military aircraft coming within 1,000 ft of each other.
US officials labelled the encounter in the South China Sea, which happened in February, “unsafe”.
Tensions have been strained following the election of Donald Trump, with the president consistently criticising China.
Before he took office he angered Beijing by holding a phone call with the president of Taiwan, the first between leaders since 1979.
Mr Trump’s stance on China is considerably tougher than the previous administration, with the billionaire blaming climate change on the Communist state.
Mr Trump has softened his stance towards the second biggest economy
Initial reports from the US air crew characterised the intercept as unprofessional
Lieutenant Colonel Lori Hodge
He has also criticised Chinas’s trade imbalance, currency policy, military expansion and support for North Korea.
And he said ahead of a meeting between himself and Chinese president Xi Jinping that it would be “a very difficult one."
White House spokesman Sean Spicer also reaffirmed the frosty relationship between the pair, saying: "He's spoken to him on the phone a few times, but we have big problems…
China deploys military vehicles towards North Korea border
China test missile guided destroyer in waters near North Korea
China launch WARSHIP as World War Three tensions rise
“Everything from the South China Sea, to trade, to North Korea.
“There are big issues of national and economic security that need to get addressed.
"There's a lot of big things that we need to accomplish with China, and I think that we will – we will work on them."
The incident is the latest in a string of defiant actions from both sides
Despite the initial rhetoric, it appears Mr Trump has softened his stance towards the second biggest economy, with a meeting between the pair seeing the president reversing some of his previous claims.
Meting last month, Mr Trump later said: “We have a very good relationship, we have great chemistry together.
“They’re not currency manipulators.”
US Vice-President Mike Pence's visit to Asia in pictures
Thu, April 20, 2017
US Vice President Mike Pence is on a ten-day visit to Asia
1 of 9
Nasarudin Umar (L) and Muhammad Muzammil Basyuni (R) show the Istiqlal grand mosque to US Vice President Mike Pence in Jakarta
His shift comes as relations between the US and Russia hit a historic low, with the president facing a probe into alleged ties between Moscow and the Trump campaign.
A special prosecutor has been appointed to take over the Justice Department’s investigation, and follows the dismissal of former FBI chief James Comey.
Deputy Attorney General Rod Rosenstein appointed former FBI Director Robert Mueller to oversee the investigation.