Japan has neither confirmed nor denied reports that its top nuclear envoy had characterized South Korea's proposal to declare a formal end to the Korean War as "premature."

When asked whether the Kyodo News report was true, Deputy Chief Cabinet Secretary Yoshihiko Isozaki said Monday the U.S., Japan and South Korea are closely exchanging views on North Korea but refused additional comment, citing diplomatic privilege.

He said Tokyo has held consultations with Washington and Seoul based on its stance and that trilateral cooperation will continue.

Citing diplomatic sources, Kyodo News said Saturday that Japan's nuclear envoy voiced disapproval of the war-ending declaration during a meeting last month in Washington with his South Korean and U.S. counterparts.

Takehiro Funakoshi reportedly said it is "premature" to discuss the proposal, citing North Korea's repeated missile launches.