Tokyo ? The United States is pushing Japan to suspend its hunt of humpback whales, and the American ambassador to Tokyo said Wednesday an agreement to stop it may have already been reached.

Japan dispatched its whaling fleet last month to the Southern Pacific in the first major hunt of humpbacks since the 1960s. Commercial hunts of humpbacks have been banned worldwide since 1966.

Word of a possible delay in the hunt came as the Australian government said it would send planes and a ship to conduct surveillance of Japanese whaling ships off Antarctica.

U.S. Ambassador Thomas Schieffer said Japanese and U.S. negotiators were working on an American demand that the hunt – part of a scientific research program allowed under international rules – be halted.

“I think we had an agreement this morning or last night between the United States and Japan that humpback whales would not be harvested, I think, until maybe the international whaling conference in June,” Schieffer said.