A document on a secret Japan-U.S. pact signed by Prime Minister Eisaku Sato and President Richard Nixon in 1969 allowing the United States to introduce nuclear weapons into Okinawa in the event of an emergency has been kept by the Sato family, a close relative disclosed Tuesday.

If the document is genuine, it would put an end to debate over the existence of the secret pact, which has long been denied by the Foreign Ministry.

It would also influence the ongoing probe by a third-party panel set up by the Foreign Ministry to look into nuclear deals between the two countries.