Okinawa Gov. Takeshi Onaga announced Monday that he has formally notified the central government he is taking steps to revoke permission for landfill work related to the plan to build a new U.S. Marine Corps facility off Henoko in Nago.

The move, though not unexpected, now makes a protracted legal battle between Okinawa and the central government likely, creating further questions about when, or even if, the replacement facility for the Futenma base will be completed.

“This is a major step to realizing my campaign promise, which was to use all available means to prevent the building of a new base at Henoko,” Onaga told reporters in the prefectural capital of Naha.

He said he made the decision after a prefecture-appointed panel looked into how and why then-Gov. Hirokazu Nakaima approved the landfill application. The panel discovered legal flaws in July that Onaga said would allow the prefecture to revoke permission.

In August, the central government announced a one-month suspension to the construction work to discuss the issue with Onaga. But by the Sept. 9 deadline, no compromise had been reached.

“Unfortunately, although I met five times with the central government and explained Okinawa’s position, the history of the bases and the feelings of the Okinawans, I got the impression that such thinking was not taken into account,” Onaga said.

In Tokyo, however, Chief Cabinet Secretary Yoshihide Suga told reporters it is the government’s position that there were no flaws in the approval process. On Saturday, the central government announced it was resuming construction, which Onaga said also affected his decision to begin the cancelation process Monday.

The next step will be a hearing Sept. 28 with the Okinawa Defense Bureau, part of the Defense Ministry, with the formal decision to revoke permission likely to come down in about a month.

What happens after that is somewhat unclear. The Defense Ministry is likely to file a complaint with the Land, Infrastructure, Transport and Tourism Ministry to try to overturn the governor’s decision. But the issue could also be headed for the courts, raising the possibility of long construction delays, additional costs and more political tensions for Tokyo, Washington and Okinawa.

For their part, Okinawans showed no sign Monday of backing down.

“We welcome the decision by the governor, and unlike the former governor, who reversed his promise to allow the new facility to be built, Onaga is keeping his word,” said Hiroshi Ashitomi, a member of a Nago-based group opposed to the project.

“We hope that the central government will respect the wishes of the people of Nago. Mayor Susumu Inamine supports Onaga’s stance and has said that if it comes to legal measures to stop the base, he’ll work with the prefecture,” said Shinichiro Nakama, a Nago official involved with base issues.

Since coming to office in November 2014 by opposing the Henoko project, Onaga and the prefectural government have lobbied against it not only in Tokyo but also in Washington.

Next week, the governor will speak to the United Nations Human Rights Council in Geneva about Okinawa’s position on the Henoko issue and its history with the U.S. military.