All eligible voters in Okinawa will be able to take part in a referendum on the relocation plan for a key U.S. air base later this month, as three cities that were opposed to it announced Friday they have changed their position.

The Feb. 24 referendum will ask people to vote on the controversial U.S.-Japan plan, with Gov. Denny Tamaki hoping its outcome, although not legally binding, will further demonstrate Okinawa’s opposition to the project.

The current ordinance on Okinawa referendums calls on governors to respect outcomes supported by at least a quarter of eligible voters.