Japan's Defense Minister Takeshi Iwaya says work to improve soft ground at the site for a planned US airbase relocation in Okinawa Prefecture could raise the project's initial estimated cost.
The Defense Ministry began dumping rocks and sand off the coast of Henoko, Nago City, last December to move the US Marine Corps Futenma Air Station there.
But the ministry found soft ground in part of the planned reclamation zone.
Iwaya said in the Diet on Wednesday that it is technically possible to reinforce the ground, but that the work may push up costs.
The ministry initially estimated the reclamation would cost about 2.1 billion dollars.
Okinawa Prefecture has put the cost of relocation at up to 23 billion dollars.
Iwaya said he believes the prefecture simply increased the ministry's estimate of reclamation costs tenfold and that the total cost may not rise that much.