The United States on Wednesday pressed its concerns over China's newly declared air defense zone, a day after American B-52s flew over the disputed area in the East China Sea.

Vice President Joe Biden will confront the Chinese leadership about the controversial issue during a pre-planned trip to Beijing next week, senior administration officials said.

"Clearly, the visit to China creates an opportunity for the vice president to discuss directly with policymakers in Beijing this issue, to convey our concerns directly and to seek clarity regarding the Chinese intentions in making this move at this time," one official told reporters.

"It also allows the vice president ... to make the broader point that there's an emerging pattern of behavior by China that is unsettling to China's own neighbors and raising questions about how China operates in international space and how China deals with areas of disagreement with its neighbors."

Announced over the weekend, the Air Defense Identification Zone (ADIZ) requires aircraft to provide their flight plan, declare their nationality and maintain two-way radio communication, or face defensive emergency measures.

The move has fueled tensions with Japan since the zone covers Tokyo-controlled islands -- known as Senkaku in Japan and Diaoyu in China -- where ships and aircraft from the two countries already shadow each other in a potentially dangerous confrontation.

Earlier Wednesday, China insisted it has the ability to enforce its newly-declared air zone over those islands.

"The Chinese government has the will and ability to defend our national sovereignty and security," Qin Gang, Beijing's foreign ministry spokesman told reporters.

The defense ministry, meanwhile, said it had "monitored" US B-52 bomber flights in its new zone, in an assertion of its authority that avoided threatening direct action.

The unarmed bombers took off from Guam on Monday on a scheduled flight in what American defense officials insist was a routine exercise.

The flight of the long-range Stratofortress planes was a clear warning that Washington would push back against what it considers an aggressive stance by Beijing.

But it was also a signal of US support for Japan, with which Washington has a security pact.

US defense chief Chuck Hagel praised Tokyo Wednesday for showing "appropriate restraint" in the wake of the announcement.

He also "reaffirmed longstanding US policy that Article V of the Japan-US Mutual Defense Treaty applies to the Senkaku Islands, and pledged to consult closely with Japan on efforts to avoid unintended incidents," according to a statement.

According to the Jiji Press news agency, Japanese Defense Secretary Itsunori Onodera and Hagel spoke by phone for 30 minutes Wednesday during which they agreed to cooperate in pressuring China to abandon the zone.

Japanese airlines, under pressure from Tokyo, stopped following China's new rules Wednesday, after initially complying.

However, according to Jiji Press, they had no problems despite not submitting their flight plans to Chinese authorities in advance.

In Washington, meanwhile, the State Department advised all US airlines to take steps to stay safe amid the fresh tensions.

Chinese officials and state media have accused Japan and the US -- which both have ADIZs -- of double standards, and argue that the real provocateur is Tokyo.

The islands dispute, which has simmered for decades, escalated in September 2012 when Japan purchased three of the uninhabited outcrops from private owners.

Beijing accused Tokyo of changing the status quo and has since sent ships and planes to the area as displays of force, prompting Japan to scramble fighter jets 386 times in the year to September.

After an unidentified drone flew towards the islands, Tokyo threatened to shoot down such aircraft, which Beijing warned would amount to an "act of war."

Biden's trip to China next week is part of a wider tour of the region and will also include stops in Tokyo and Seoul.

While in Beijing, he will meet with President Xi Jinping, Vice President Li Yuanchao and Premier Li Keqiang.

"He's going to have a very high-level and a very wide-ranging dialogue with the senior Chinese leadership that covers a wide range of shared interests along with areas of concern, areas of cooperation and areas of deconfliction," the US official added in previewing the visit.