A senior U.S. government official has suggested that the U.S. and Japanese governments may postpone finalizing new defense cooperation guidelines until next April, months after the current year-end deadline.

The official said the U.S. military sees the need for further consultation between Tokyo and Washington to craft new guidelines that detail how the Self-Defense Forces will work alongside the U.S. military under a controversial reinterpretation of the Constitution that would allow the SDF to exercise the right of collective self-defense.

The two countries will hold so-called "two-plus-two" security talks involving their foreign and defense ministers when they devise the final version of the guidelines, the official said on condition of anonymity.

In an interim report released earlier this month, Japan and the United States simply said, without elaboration, the revised guidelines will "appropriately" reflect the Cabinet decision this summer to reinterpret Japan's pacifist Constitution to permit the nation to come to the aid of allies under armed attack.

"We don't need to put the whole thing in the (new) guidelines, but we need to have something about the activities of the SDF," the U.S. official said Monday.

The Japanese and U.S. governments agreed in October last year to rewrite the guidelines, which were last updated in 1997, by the end of this year, citing the need to address changes in the security environment in the Asia-Pacific region.

Unnamed sources on the Japanese side suggested late last month that Tokyo was exploring the possibility of postponing the defense guidelines revision until at least early next year, in a bid to help keep the ruling coalition in the Diet aligned over new security policy legislation.