The United States recognized the South Korean-controlled Takeshima Islands in the Sea of Japan as Japanese territory as of 1950, a research report released by the Japanese government showed Tuesday.

Drawing on Australian government documents, the report says the United States showed its recognition of the status of the islands, which are known as Dokdo in South Korea, when it started informal talks with other countries to create a draft for the San Francisco peace treaty.

“It is thought that … Takeshima … long recognized as Japanese, would be retained by Japan,” the U.S. told Australia, according to the report.

The report also shows a document stored at the National Archives of Japan that cited a Cabinet decision to incorporate Takeshima into Shimane Prefecture in 1905.

It also includes eight sets of documents showing the incorporation of the Senkaku Islands in Okinawa Prefecture into the prefecture’s Yaeyama County in 1902. The islands are claimed by China.

The Cabinet Secretariat outsources the research to a private company on an ongoing basis, and has released survey results every year since fiscal 2014.