TOKYO — An impending judicial setback has left Okinawa Gov. Takeshi Onaga reaching for other ways to keep his promise to thwart the relocation of a U.S. military base.

A grim-faced Onaga told reporters Monday that he would abide by the Supreme Court ruling, which is expected to come Dec. 20, and retract his cancellation of approval for landfill work necessary to replace the U.S. Marine Corps’ Futenma air base.

“It’s not a matter to be put off,” Onaga said. “I’ll make a decision at the proper time.”

This does not mean Onaga has given up on his vow to do all he can to stop the central government from moving the Marines from Futenma to a new coastal airfield at Henoko. He is prepared to keep using his powers as governor to delay construction as much as possible.

One option being considered by the prefectural government is declining to renew a permit for coral reef destruction that is due to expire at the end of March. This would bring work by the Ministry of Defense’s Okinawa bureau, which is overseeing the construction, to a standstill.

The governor would also need to sign off on any changes to the initial work plans. “Naturally, we have to strictly apply legal and regulatory requirements when it comes to other procedures,” Onaga said, reminding Tokyo of such a possibility.

Onaga won the November 2014 gubernatorial election on a platform against the Henoko relocation. Much of his support base consists of groups that firmly oppose the presence of U.S. forces, including the Japanese Communist Party and the Social Democratic Party, making it difficult for him to compromise with Tokyo.

Some opposition lawmakers in the prefectural assembly are looking to turn up the heat on Onaga. “This will be a major turning point,” a senior Liberal Democratic Party lawmaker said. “Even if he keeps opposing [the move] despite the ruling, his support won’t broaden.”