The U.S. military has flown two unarmed B-52 bombers through airspace over disputed islands in the East China Sea, defying an attempt by China to wrest control of the territory from Japan.
The Pentagon said the Monday flights did not trigger a response from Beijing, which two days earlier declared the airspace part of a new air defense zone. China warned all aircraft to identify themselves before entering the area and to obey all orders from Beijing.
China published coordinates for the so-called East China Sea Air Identification Zone on Saturday and warned it would take emergency defense measures to enforce its claim.
The White House on Tuesday urged Beijing to settle its maritime dispute with Tokyo, without "threats or inflammatory language."
The flights over the uninhabited islands - known as Senkaku in Japan and Daioyu in China - come one week before U.S. Vice President Joe Biden is scheduled to visit Beijing as part of a week-long trip to the Asia-Pacific region.
Biden is expected to voice U.S. concerns to Chinese officials about the increasingly tense situation, which comes as Beijing seeks to lay claim to large swaths of the East and South China seas.
Japan annexed the islets in the late 19th century, while China claimed sovereignty over the archipelago in 1971. Beijing linked its claims to ancient maps it says shows the territory has been Chinese for centuries.
The festering China-Japan dispute is one of several maritime controversies pitting China against Southeast Asian nations, including the Philippines, Vietnam, Brunei and Malaysia.
Beijing has indicated a willingness to negotiate the disputes, but has so far rejected calls for multilateral talks. It has sought separate talks with each country.
Japanese Defense Minister Itsunori Onodera said Tuesday that Tokyo is working closely with Washington and will take all necessary steps to protect what it insists is Japanese territory.