A U.S. expert on Japan has warned that U.S. Marine Corps Air Station Futenma in Ginowan, Okinawa, will remain as is if no replacement base is built in the prefecture in line with a plan agreed upon by Washington and Tokyo, an expert said Wednesday.

The expert expressed this view in a Tuesday meeting in Washington as Okinawa Gov. Hirokazu Nakaima considers whether to permit the central government to begin filling in offshore areas to accommodate the runways of the planned replacement airstrip on the Henoko coast of Nago, farther north on Okinawa Island from the crowded city of Ginowan.

Participants in the meeting included Michael Green, a former staff member of the National Security Council; Rust Deming, former chief of the State Department's Office of Japanese Affairs; and Katsuyuki Kawai, a member of the ruling Liberal Democratic Party who formerly headed the House of Representatives Foreign Affairs Committee.

The governor is opposed to the plan to build a Futenma replacement base in Okinawa, which already hosts the bulk of U.S. military facilities in Japan, and wants the current base closed.

The U.S. expert, who was not identified, was quoted as telling the meeting that the Futenma base will "stay" in densely populated Ginowan if Nakaima fails to green-light the government's plan to reclaim land off Henoko.

That is not what the U.S. side wants to see, but there is no other option than the Henoko replacement facility, the expert said in the meeting.

The Japanese and U.S. governments are working on implementing the relocation plan basically in line with their 2006 bilateral accord. But the project has hit a snag due to strong opposition by Nakaima and other local leaders.