The White House statement came hours after the Chinese Defense Ministry issued a map of an East China Sea Air Defense Identification Zone (ADIZ) that includes a chain of islands also claimed by Japan. The map’s release also triggered a protest from Tokyo.
Beijing issued a set of rules for the zone, saying all aircraft in the area must notify Chinese authorities and are subject to emergency military measures if they do not identify themselves or obey orders from Beijing. The Chinese government said it would "identify, monitor, control and react" to any air threats or unidentified aircraft approaching from the sea.
The rules went into effect Saturday.
"This unilateral action constitutes an attempt to change the status quo in the East China Sea. Escalatory action will only increase tensions in the region and create risks of an incident," Secretary of State John Kerry said in a State Department news release emailed to Al Jazeera.
"We don't support efforts by any State to apply its ADIZ procedures to foreign aircraft not intending to enter its national airspace," Kerry said. "We have urged China to exercise caution and restraint, and we are consulting with Japan and other affected parties, throughout the region."
The White House issued a similar statement, saying the U.S. was "concerned" that China’s move would worsen tensions in the region. Defense Secretary Chuck Hagel said the zone will not "change how the United States conducts military operations in the region.”
In Tokyo, Junichi Ihara, head of the Foreign Ministry's Asian and Oceanian Affairs Bureau, protested by phone to China's acting ambassador to Japan, Han Zhiqiang, saying the zone is "totally unacceptable," according to a ministry statement.
Ihara also criticized China for "one-sidedly" setting up the zone and escalating bilateral tensions over the islands.
Both Beijing and Tokyo claim the islets, called Diaoyu in Chinese and Senkaku in Japanese. Protests erupted throughout China last year to denounce the Japanese government's purchase of the islands from private ownership.
A rising economic and military power, China has become more assertive over its maritime claims. It has been in disputes with several neighboring countries over islands in the East and South China seas.
"By establishing the air defense zone Beijing has ... potentially escalated the danger of accidental collisions between the Chinese military and the U.S. and Japanese counterparts," said Tomohiko Taniguchi, a counselor in the office of Japanese Prime Minister Shinzo Abe. "It poses a serious challenge against freedom of movement in the sky and in the seas."
China said the zone is in line with the practice of other nations that have similar zones to protect their coasts. The new zone overlaps with Japan's existing one, which also includes the disputed islands.
"This is a necessary measure taken by China in exercising its self-defense right," Chinese Defense Ministry spokesman Yang Yujun was quoted as saying on the ministry's website. "It is not directed against any specific country or target. It does not affect the freedom of over-flight in the related airspace."
Other governments including Taiwan also have territorial claims that overlap with China’s in the region.