The US called on China to scrap its newly declared air defence identification zone on Monday, warning that Beijing risked a potentially dangerous confrontation with Japan and its allies at the start of a trip to the region by vice-president Joe Biden.

The explicit request for China to “rescind” threats against unannounced aircraft passing over a chain of islands in the East China sea was made by the US just hours after Biden landed in Tokyo ahead of a six-day trip to Japan, China and South Korea.

“The fact that China’s announcement has caused confusion and increased the risk of accidents only further underscores the validity of concerns and the need for China to rescind the procedures,” said Jen Psaki, the chief spokesperson for the State Department.

Biden, who was met at Tokyo airport by Caroline Kennedy, the daughter of former president John F Kennedy and recently appointed ambassador to Japan, is expected to attempt to defuse the controversy during his visit.

Senior diplomats privately concede that the dispute over the airspace above the islands, known as the Senkaku in Japan and the Diaoyu in China, will almost entirely dominate Biden’s trip, which had been intended to focus on US economic interests in the region. The row began nine days ago when Beijing unilaterally declared the enlarged air defence identification zone.

The Chinese defence ministry ordered all aircraft flying through the zone to notify Chinese authorities in advance, warning that it would "identify, monitor, control and react to" any air threats or unidentified flying objects coming from the sea.

“That kind of coercive, strong language is worrisome, and we hope it is not tested,” a senior government official from the region told the Guardian, echoing growing concern about the possible risk of an accidental confrontation that spirals out of control.

The official said one possible scenario would see military aircraft scrambled simultaneously by China and the US, and possibly Japan too, meeting in the air. Another would be that China feels the need to intercept an aircraft that enters the contested airspace without prior notice.

“Mishaps and miscalculations can happen, particularly if aircraft are scrambled to intercept an aircraft. You never know how these situations can unfold.”

Japanese airlines passing through the military zone declared by China are not currently informing Beijing of their flight plans. However, aircraft associated with other countries, including those flown by US and South Korean airlines, are submitting information to the Chinese, after domestic civil aviation authorities advised it was in the interest of safety.

Psaki stressed that the guidance to airlines from the Federal Aviation Authority “in no way indicates” US acceptance of China’s declaration. She said China had made the declaration “in an uncoordinated fashion” which was “inconsistent with standard practice”, adding the US did not believe the declaration to be legitimate.

Her remarks were echoed by the White House. "This is about the safety and security of passengers and is not, in any way, indication of a change in our position,” said spokesman Jay Carney. “This appears to be a provocative attempt to unilaterally change the status quo in the the East China sea and thus raises tensions and increases the risk of inadvertent confrontation.”

On Tuesday the Chinese envoy to the Philippines added to tensions, saying Beijing had a sovereign right to establish a maritime air defence zone over other regions. When asked to comment about concerns that China might set up a similar zone over the South China Sea – where it has disputes with the Brunei, Malaysia, the Philippines, Taiwan and Vietnam – Ma Keqing said it was the Chinese government's right to decide "where and when to set up the new air identification zone".



Ma said the East China Sea zone's designation "will not hinder any normal freedom of flights within this area if they've notified the Chinese authorities".

The US ambassador to Manila, Philip Goldberg, described China's move as dangerous. "We do not believe that this is a move intended to build confidence or in any other way improve the situation," he said. Instead, China's new zone "will create tension and the possibility of miscalculations and that's never good".

Biden, who arrived in Japan late on Monday night, is now tasked with delicate role of attempting to cool tensions. “I believe this latest incident underscores the need for agreement between China and Japan to establish crisis management and confidence-building measures to lower tensions,” the vice-president said in an interview with Japan’s Asahi Shimbun newspaper on the eve of his arrival.

Washington has not taken a formal position on the sovereignty of the islands. However, it recognises Tokyo's administrative control, and said explicitly last week that its treaty to defend Japan militarily applies to territory around the islands.

The US, in its most direct challenge to Chinese military endeavours in two decades, flew two B-52 bombers through the zone without notifying the Chinese. The US navy has sent P-8 Poseidon patrol aircraft to Japan, a long-planned move that gives the allies greater ability to track hostile submarines and other naval ships in Japanese waters.

Following Washington’s lead, Tokyo has sent military aircraft, including F-15 fighter jets and Awacs surveillance planes, directly through the claimed Chinese zone. For Japan, which has recently reopened debate on its formal post-second world war pacifist defence policies, it has been a notably aggressive response.

However the decision by US aviation authorities to advise airlines to comply with China’s requests has roiled Japan, despite Washington’s repeated insistence last week that its commitment to Japanese security is beyond question. The Japanese TV station NHK quoted a former senior foreign ministry official, Yukia Okimoto, saying the US “hurt Japan’s interests over an issue related directly to Japan’s national security in a way visible to the whole world”.

Shinzo Abe, the Japanese prime minister, said he would “deal with the matter by co-ordinating closely” with Biden, who will visit Beijing on Wednesday and meet with China’s president Xi Jinping. The vice-president is known to have a particularly good relationship with Xi, formed over several years.

Biden’s trip enables him to have face-to-face contact with all the regional players with a stake in the controversy, including South Korea, where he will spend two days meeting senior government officials at the end of the week.

South Korea, which has strained relations with Japan, is also being sucked into the dispute. Local reports indicate that Seoul is in the final stages of expanding its own six-decade-old air defense identification zone southward, which would overlap with territory claimed by China.

The move comes after a defense consultation last week between China and South Korea failed to reassure Seoul that China’s expanded zone was aimed exclusively at Japan.

The senior government official said one unintended consequence of China’s declaration could be that Japan and South Korea, rivals undergoing a particularly strained relations at the moment, will be brought closer together. The official said the two countries were expected to “compare notes” over how to respond to China’s move – and high-level meetings between the two countries remain a possibility.

It is unclear if Biden will attempt to mediate between China, Japan and South Korea. Aides to the vice-president told reporters last week that Biden would seek only “clarity” from China about its military intentions, but declined to say that he would call for China to reverse its declaration, which Japan is seeking.

China has thus far shown no signs of retreating over the zone. It announced that it scrambled its own fighter jets in the air defence identification zone on Friday, an intended challenge to the US and Japan. But the Japanese defense ministry sharply questioned whether the Chinese jets ever actually passed through the zone, issuing a statement saying it spotted no additional air traffic in the area.

Additional reporting by Dan Roberts