China says it monitored defiant US bomber flights

China acknowledged Wednesday it let two American B-52 bombers fly unhindered through its newly declared Air-Defense Identification Zone in the East China Sea despite its earlier threat to take defensive measures against any unidentified foreign aircraft.

The flights followed days of angry rhetoric and accusations over Beijing's move, which some experts say is designed to assert Chinese sovereignty over Senkaku/Diaoyu — uninhabited islands, also claimed by Japan, whose nearby waters are rich in natural gas, oil and fish.

The Chinese Defense Ministry said on Saturday they would take "defensive emergency measures" against any planes failing to identify themselves, provide their flight plans or maintain two-way radio communication.

On Tuesday the U.S. flights tested the Chinese zone for the first time since it was declared over the weekend, and China's muted response raised questions about Beijing's determination to enforce its requirements. China's lack of action suggested to some analysts that it was merely playing out a diplomatic game to establish ownership over the area rather than provoke an international incident.

There are no clear international laws governing Air-Defense Identification Zones, Bonnie Glaser, Asia expert at the Center for Strategic and International Studies, told Al Jazeera. The zones, she said, are demarcated by mostly "random" borders in accordance with the strategic objectives of a country.

While many countries — including the U.S., Japan, South Korea, Vietnam and Taiwan — have self-declared Air-Defense Identification Zones already, China's announcement angered its neighbors, experts say, because it was done suddenly, without consultation and includes disputed territories. The Chinese announcement also appears to apply to all aircraft, and not just those flying into its official airspace, which is the international norm for Air-Defense Identification Zones.

Rory Medcalf, director of the International Security Program at the Lowy Institute, wrote on Wednesday: "If China’s new zone did not include disputed maritime territory, if its requirements for compliance applied only to aircraft heading into Chinese airspace, and if neighbours like Japan and South Korea had been consulted ahead of the announcement, then there would be little or nothing for others to object to."

The U.S., Japan, South Korea and Taiwan have all refused to acknowledge the zone.

Vice President Joe Biden will raise American complaints about the Chinese declaration when he visits the country next week, senior administration officials said on condition their names not be used.

State Department spokeswoman Jen Psaki said that U.S. civilian air carriers were being advised "to take all steps they consider necessary to operate safely in the East China sea region." But Psaki did not specify what those steps might be and stopped short of saying airlines should provide flight details to Chinese authorities.

Japanese airlines, after initially indicating they would comply with Chinese information requests, have since said they are ignoring China's directives. South Korean airlines are also declining to submit their flight plans to China, according to the Wall Street Journal.

Asked repeatedly about the incident at a regularly scheduled briefing, China's Foreign Ministry spokesman Qin Gang said it had been handled according to procedures laid out in the Saturday statement but offered no specifics.

"Different situations will be dealt with according to that statement," Qin said.

The U.S., which has hundreds of military aircraft based in the region, described the flights as a training mission unrelated to China's announcement of the zone. U.S. officials said the two unarmed B-52 bombers took off from their home base in Guam around midday and were in the zone that encompasses the disputed islands for less than an hour before returning to their base, adding the aircraft encountered no problems.

The bomber flights came after the State Department's Psaki said China's move appeared to be an attempt to change the status quo in the East China Sea.

"This will raise regional tensions and increase the risk of miscalculation, confrontation and accidents," she told reporters.

The Pentagon said Defense Secretary Chuck Hagel discussed the situation by telephone on Wednesday with his Japanese counterpart, Itsunori Onodera, and Hagel said U.S. military operations "will not in any way change as a result of China's announcement."

Hagel reiterated that the "U.S.-Japan Mutual Defense Treaty applies to the Senkaku Islands."

The American decision to fly bombers into the disputed area, however, may have been made to deter Japan, not China, from making any belligerent moves that could aggravate the already tense situation, said Anne-Marie Slaughter, president of the New America Foundation, Bloomberg News reported.

"We are saying to Japan, 'Do not respond, we are here,'" Slaughter said on Monday.

Chinese reaction to the U.S. bomber flights was predictably bitter, with some recalling the 2001 collision between a Chinese fighter and a U.S. surveillance plane in international airspace off China's southeastern coast — the kind of accident some fear China's new policy could make more likely. The Chinese pilot, Wang Wei, was killed in the crash and the U.S. crew forced to make a landing on China's Hainan island, where they were held for 10 days and repeatedly interrogated before being released.

"Let's not repeat the humiliation of Wang Wei. Make good preparations to counterattack," wrote Zheng Daojin, a reporter with the official Xinhua News Agency on his Twitter-like Weibo microblog.

It wasn't clear whether Beijing had anticipated the response from Washington and others, or how well it is prepared to back up its demands.

Chinese scholars, who often serve as ad-hoc government spokesmen, criticized Tuesday's flights as a crude show of force and said Beijing wasn't looking for a fight.

"It's not that China didn't want to enforce its demands, but how do you expect China to react?" said Zhu Feng, an international security expert at Peking University.

Lisa De Bode contributed reporting. Wire services.