To that end, Biden said he would raise those concerns with China's leaders "with great specificity" during his Beijing visit.
As if to make a point that the newly declared air defense zone will be a major topic of Biden's talks with the Chinese, China's Defense Ministry issued a statement reiterating the country's determination to enforce the zone just as the vice president was arriving in Beijing on Wednesday. China's military is "fully capable of exercising effective control" over the area covering the disputed islands in the East China Sea, said ministry spokesman Geng Yansheng.
Although the U.S. has repeatedly said it rejects the zone, Biden has avoided calling publicly for Beijing to retract it, wary of making demands that China is likely to snub. Rather, the U.S. hopes that with enough pressure, China will refrain from strictly enforcing the zone, essentially nullifying it for practical purposes.
What's more, the U.S. wants to show that the diplomatic consequences for such actions are severe enough that China will think twice in the future about asserting its authority in such heavy-handed ways. Already, China has claimed it has a sovereign right to establish a similar zone over the South China Sea, where China and the Philippines are locked in another long-running territorial dispute.
The East China Sea zone covers more than 600 miles from north to south above international waters separating China, South Korea, Japan and Taiwan. China says all aircraft entering the zone must notify Chinese authorities beforehand or face unspecified defensive measures.
The new round of tensions with China comes as the U.S. is striving to increase its own engagement, influence and military presence in Asia, in part as a hedge against China's growing power. But the Obama administration has said it's pursuing a new model for engagement with China, where the two countries can cooperate economically while maintaining a healthy competition.
"There is a mistrust here by China of U.S. intentions," Sen. Ben Cardin, D-Md., who chairs the Senate's Asia panel, said in an interview. "China is not clear why the U.S. is interested in Asia. They think it may be to affect China's development in a negative way and nothing could be further from the truth."
It wasn't always this way.
When Biden came to China two years ago, Xi brought him far away from Beijing's congested streets and sober government buildings to Chengdu, an ancient city in lush southwestern China. At the end of a long day of touring, the two set off for a stroll to view an irrigation site built by the Qin Dynasty in 256 B.C. and still used today.
Walking with Biden along an ornately painted walkway overlooking the canal below, Xi had ditched his jacket a rare departure from the stiff formality traditional of Chinese officials.
Aides traveling with Biden said it was moments like these that offered some of the first clues that Xi, now China's president, might be different. During hours spent with Biden on the road, Xi began to reveal a bit about his personal style, giving the American delegation a glimpse into how he might one day rule the world's second-largest economy and a potential U.S. rival.
Knowing Xi was poised to eventually become president, the White House had turned to Biden to feel him out during a pair of official visits while Xi was still vice president. The goal was to make an early down payment on a relationship that would surely be critical as China gained political and economic clout on the world stage.
"If you look at Xi Jinping's personality, he seems to really demonstrate some aspects of Chinese traditional culture. You give high regard to personal trust," said Li Mingjiang, a China expert at Singapore's Nanyang Technological University. "Not a formal or legal commitment per se, but in Chinese culture, a lot of things can be done simply on trust."
Whether that trust can serve as a basis for Biden and Xi to de-escalate tensions during Biden's stop in Beijing remains to be seen. Unlike Biden's last trip to China, this visit will have few of the casual moments or long get-to-know-you sessions that also characterized Xi's 2012 visit to the U.S., where he visited small-town Muscatine, Iowa, and spent hours with Biden in Los Angeles.
Before departing China on Thursday, Biden will have breakfast with American business leaders and meet with China's premier, Li Keqiang. The vice president will then fly to Seoul, South Korea, for the final leg of his trip.
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Reach Josh Lederman at http://twitter.com/joshledermanAP