In 1971, the year the archives cover, a backroom deal was signed by the United States and Japan, with China excluded from the talks.

The Okinawa Reversion Agreement required the US to return the "administration" of Okinawa to Japan, but the document integrated the Diaoyu Islands — a Chinese territory and geographically part of Taiwan — into Okinawa. The Chinese Government has never recognized the agreement.

However, according to Japan's Kyodo news agency, the newly released documents said Chinese Taiwan "started its claim" over the islands in 1971, indicating a denial of China's centuries-long sovereignty over them.

The archives said the then-Japanese Foreign Minister Kiichi Aichi demanded that Taiwan tone down the islands issue and avoid stirring up the Japanese public "at the critical period of time" when the Okinawa Reversion Agreement was being considered. In return, Japan would support Taiwan's efforts to keep its seat at the United Nations.

Japan has a record in recent years of denying its political consensus with China on putting aside the islands dispute, which was reached when the two countries normalized diplomatic relations in 1972.