Japan and the U.S. failed to agree on where to move the helicopter operations of the U.S. Marines Corps Futenma Air Station in Okinawa during senior working-level talks between the two nations that just ended in Washington, Foreign Minister Nobutaka Machimura said Friday.

"I do not know if it is appropriate to say (there was a) considerable (gap), but there is a difference of opinion," Machimura told reporters after a Cabinet meeting, identifying the "Futenma relocation" as the key pending issue in the U.S. realignment talks.

The defense and foreign affairs officials discussing the realignment of U.S. forces in Japan ended their three-day, unofficial talks Wednesday without coming to an agreement.

The Futenma relocation is a key issue in the overall bilateral talks for crafting a comprehensive package on the U.S. realignment.

Separately, Defense Agency Director General Yoshinori Ono expressed regret Friday that the two sides failed to reach an agreement, while Chief Cabinet Secretary Hiroyuki Hosoda said he does not think the talks were a failure because the negotiation process is still ongoing.

"There are one or two matters" that need to be settled, Ono said, apparently alluding to the Futenma issue.

Both Ono and Hosoda expressed hope that an interim report on the realignment of U.S. forces in Japan could be compiled by month's end.