Some parts of Okinawa may not participate in a local referendum on a controversial relocation plan for a U.S. air base within the island prefecture after its assembly failed to unanimously pass a resolution Tuesday.

After some municipalities in the prefecture opposed a plan to have voters cast ballots of only "yes" or "no" on the U.S. Marine Corps Air Station Futenma's relocation in the Feb. 24 referendum, the assembly adopted a draft of the revised ordinance by a majority vote allowing the residents to vote "neither."

The mayors of five cities are against the referendum unless the revision to the ordinance is approved unanimously, arguing local people have various opinions on the issue.