The governor of Okinawa has not approved by Wednesday's deadline a revision to the Japanese government's landfill project for the relocation of US military base within the southwestern prefecture.

Tokyo plans to move the US Marine Corps Futenma Air Station from the densely populated city of Ginowan to an offshore site at Henoko in Nago City.

But the ground of the site slated for reclamation was found to be too soft.

The central government then applied for permission from the prefecture to revise the plan and carry out reinforcement work.

Last month, Japan's Supreme Court turned down Okinawa's appeal of a high court decision upholding the central government's directive for the prefecture to approve changes to the reclamation plan.

Okinawa is obligated to approve the project in line with the central government's instructions.

Tokyo had set Wednesday as the deadline for approval by Governor Tamaki Denny.

But Tamaki told reporters at around 5:00 p.m. he needs to study the top court's ruling in detail, and must also analyze various opinions from the people of Okinawa and scholars to ensure stable prefectural administration.

Prime Minister Kishida Fumio says he'll continue efforts to realize the relocation.

"I am working to move the Futenma Air Station as soon as possible so people in Okinawa can feel safe," Kishida said.

The central government is expected to ask a court for permission to begin procedures to issue an approval in what is called execution by proxy.