BEIJING  - China’s new air defense identification zone over the East China Sea has caused “significant” unease in the region, US Vice President Joe Biden said on Thursday, adding he had stated Washington’s firm objection to the move during talks in Beijing.

Biden had around five hours of discussions with President Xi Jinping on Wednesday, with both leaders laying out their perspective on an issue that has rattled East Asia. The zone, two thirds the size of Britain, covers an area that includes islands at the heart of a territorial dispute with Japan.

In response, China’s Foreign Ministry said Biden had been told the zone accorded with international law and that the United States should respect it.

“China’s recent and sudden announcement of the establishment of a new air defense identification zone has, to state the obvious, caused significant apprehension in the region,” Biden told a gathering of US executives in Beijing. “I was very direct about our firm position and our expectations in my conversations with President Xi.”

Beijing’s announcement of the zone on November 23 has triggered protests from the United States, Japan and South Korea.

Under its rules, all aircraft have to report flight plans to Chinese authorities and maintain radio contact. US, Japanese and South Korean military aircraft have breached the zone without informing Beijing. China’s military has scrambled fighter jets on at least one occasion to monitor. Japanese and South Korean commercial carriers have also been told by their governments to ignore the rules. Three US airlines, acting on government advice, are notifying China of plans to transit the zone. Xi took on board what Biden said, according to a senior US administration official travelling with the vice president.

“From our perspective, it’s up to China. And we’ll see how things unfold in the coming days and weeks,” said the official.

China has repeatedly said the zone was designed to reduce the risk of misunderstandings, and stressed that since it was set up there had been no issues with freedom of flight for civilian airlines.

“During the talks (with Biden) the Chinese side repeated its principled position, stressing that the Chinese move accorded with international law and practice and that the US side ought to take an objective and fair attitude and respect it,” Foreign Ministry spokesman Hong Lei said in a brief statement.

The United States has made clear it will stand by treaty obligations that require it to defend the Japanese-controlled islands, but it is also reluctant to get dragged into any military clash between rivals Japan and China.

Japan’s Chief Cabinet Secretary Yoshihide Suga, speaking in Tokyo, rebuffed suggestions that Washington’s decision not to publicly ask Beijing to rescind the zone meant the United States was out of sync with Japan.

Biden said Washington had an enormous interest in what happens in the region.

“The United States has a profound stake in what happens here because we need, and we are, and we will remain a Pacific power, diplomatically, economically and militarily,” he said.

China’s stake in regional stability would also continue to grow, Biden added.

“That’s why China will bear increasing responsibility to contribute positively to peace and security. That means taking steps to reduce the risk of accidental conflict and miscalculation ... and refraining from taking steps that would increase tension,” Biden said.

The official English-language China Daily said the two countries had to address a serious “trust deficit”.

“The US’ reaction to the (zone) is only the latest reminder of how difficult it is for the two nations to overcome their distrust,” it said in an editorial.

But the fact neither Biden nor Xi mentioned the zone in front of reporters on Wednesday was a positive sign that both are “indeed capable of managing their occasionally volatile ties”, it noted.

Biden heads to South Korea later on Thursday, but will meet Chinese Premier Li Keqiang before he leaves.