A declassified document in a U.S. presidential library has confirmed there was a secret 1960 bilateral agreement allowing the United States to use its bases in Japan without prior consultation with Tokyo in the event war breaks out again on the Korean Peninsula, according to a researcher.

Tokyo, however, maintains no such pact exists and prior consultations are necessary.

The existence of the accord, formulated when Japan and the U.S. revised their security treaty, has long been known. But this is the first time a document verifying it has been unearthed.