The government said Tuesday it will start earth-filling work on Aug. 17 at a planned U.S. military base site in Okinawa Prefecture.

The Defense Ministry’s Okinawa Defense Bureau notified the prefectural government of the scheduled work in Nago in the Henoko coastal area, the relocation site of U.S. Marine Corps’ Air Station Futenma, located in Ginowan.

The earth-filling work will make it far more difficult to restore the site to its original state. The central government began work to build seawalls for the base in April last year.

Okinawa Gov. Takeshi Onaga, who is opposed to the relocation, told reporters his determination to block the construction of the base in Henoko has never been shaken.

The defense bureau’s notification was based on a local ordinance to prevent the outflow of red clay and other substances into the sea.

The prefectural government has 45 days to examine whether the plan is appropriate under the ordinance. But it has no authority to order the central government to cancel the plan.

Possible actions Onaga may take include revoking his predecessor’s approval for land reclamation in Henoko in order to protect coral reefs.

“If the situation gets to the point where we can’t ignore (it), I’ll withdraw the approval without hesitation,” Onaga said.

If the governor revokes the approval, Tokyo will consider legal measures, sources said.