TOKYO >> The governor of the southern Japanese island of Okinawa ordered a Defense Ministry branch to suspend all work at the site where a key U.S. military air base is to be relocated, in a growing confrontation between the island and the central government.

Gov. Takeshi Onaga told a news conference Monday that a concrete anchor thrown into the sea for a drilling survey of the reef at the designated site is believed have damaged coral.

It was his first specific action to interfere with the relocation since taking office four months ago after winning an election over a predecessor whose approval of the plan had allowed the Defense Bureau to begin preparing the site known as Henoko for eventual transfer of the U.S. Marine Corps Air Station Futenma.

Onaga said the use of concrete blocks was not part of the initial approval and was unauthorized. He said the prefecture needs to conduct its independent survey to assess the damage, and demanded the Defense Bureau stop all activity related to the relocation within one week, or revoke the license for the drilling work, which could put the entire relocation on hold.

The central government’s effort to gain Okinawa’s understanding is "insufficient," he said. "I urge the Defense Bureau to take the order seriously and take a responsible step."

It was not immediately clear whether his order would be observed.

Chief Cabinet Secretary Yoshihide Suga told a news conference that officials are currently studying the suspension order, but that the survey should proceed regardless of the governor’s order. He criticized Onaga for one-sidedly changing the concession that Okinawa had made under its previous leadership.

"I don’t see any reason why we should halt the operation," Suga said. "This is a law-abiding nation. It is extremely regrettable that (Onaga) submitted the document (ordering the suspension) at this stage."

The Futenma base now is in a densely populated part of the island, and the transfer is intended to address safety and nuisance concerns of the population. But many people on Okinawa want Futenma moved completely off the island. Opponents also say the construction would endanger the coral reef, tropical fish and other marine life.

The underwater drilling, which had been halted ahead of the November election in an apparent attempt by Tokyo to avoid controversy, resumed earlier this month, to prepare for the land reclamation needed to build an airstrip over the water from Camp Scwab, another American military base.

The Futenma relocation to Henoko is part of a broader realignment of the U.S. military presence in Okinawa, home to about half of 50,000 American troops based in Japan under a bilateral security treaty. The relocation plan, agreed upon in 1996, has been delayed as previous plans had failed.

Prime Minister Shinzo Abe’s government has repeatedly said the plan is crucial to Japan’s military alliance with the U.S. amid China’s military rise and North Korea’s nuclear ambitions.