The United States and Japan will lobby against China's recently established air defense identification zone during a U.N. civil aviation conference currently being held in Montreal, Japanese government sources said Wednesday.

The two countries plan to express their disapproval of the ADIZ during the late stage of the International Civilian Aviation Organization's council meetings around mid-March to discuss civil aviation safety measures, the sources said.

They hope the move will block China's attempt to make its ADIZ, which covers a large area of the East China Sea, an established fact. The zone includes part of the airspace over the Japanese-controlled Senkaku Islands, which China claims and calls Diaoyu.