The new East China Sea Air Defense Identification Zone (ADIZ) announced by China on Saturday has drawn a mixed response.

Chinese Foreign Ministry spokesman Qin Gang reiterated in Beijing on Tuesday that foreign international airlines' normal flight activities in the East China Sea ADIZ will not be affected.

"China will take corresponding action in accordance with the situation and the level of threat that it may face," Qin said when asked if China will not rule out resorting to the use of armed forces.

On Tuesday, two long-range US bombers conducted a routine training mission through airspace claimed by China as its ADIZ, reported the New York Times, quoting Pentagon officials.

Pentagon officials said the pair of B-52s carried out a mission that had been planned long in advance of the Chinese announcement last weekend. They made a round-trip flight from Guam, passing through a zone that covers sea and islands that are the subject of a sovereignty dispute between China and Japan, according to the report.

Anne-Marie Slaughter, president and CEO of the New America Foundation, said on Tuesday that it is possible that the US move is aimed at Japan as much as at China.

"We're saying to China: Don't think you can do this in respect to Japan and we'll not be there. But we're also saying to Japan: Do not respond. We're here," Slaughter told a seminar on US foreign policy challenges in Obama's second term held in Washington on Tuesday.

"That's very important. In another words, we do not want Japan to respond in a way that could escalate," said Slaughter, who was policy planning director at the US State Department from 2009 to 2011.

Shen Dingli, professor and director of the Center for American Studies at Fudan University in Shanghai, believes that the visit to China next week by US Vice-President Joe Biden is important to dispel distrust regarding a host of issues such as US rebalancing to Asia, the dispute over Diaoyu Islands and now the East China Sea ADIZ as well.

"It's crucial that the two countries discuss and dispel possible new distrust," he said.

The US State Department reported that Deputy Secretary of State William Burns will meet Chinese Vice Foreign Minister Liu Zhenmin, who in responsible for Asia, treaty and law and ocean affairs, in Washington on Wednesday morning. It did not say whether the meeting is related to the row arising from the ADIZ or the upcoming Biden visit.

While the Japanese government has opposed China's announcement of the ADIZ, two Japanese airlines — ANA Holdings Inc and Japan Airlines Co — have since Sunday both informed China about their flights that pass through the area, Japan's Kyodo News Agency reported.

The two airlines have reported relevant information — including flight numbers, routes and cruising altitudes of the airplanes and flight times — to Chinese authorities when flying over the Diaoyu Islands, the agency reported.

However, Japanese Chief Cabinet Secretary Yoshihide Suga said on Tuesday that the transport ministry has told the airlines that Tokyo does not recognize China's move.

Japanese Transport Minister Akihiro Ota said the government will tell China that Japan will not change its administration of airspace above the high seas, adding that the ministry hopes airline companies will make appropriate decisions based on this stance.

In addition to the recognition from Japanese companies, civil aviation officials from the Republic of Korea and Singapore have said that their airliners entering the zone will submit information to Chinese aviation authorities.