TOKYO, March 12  -- Japan's Defense Ministry resumed its drilling survey Thursday into the seabed in a coastal region of Okinawa Prefecture, set to be the site of a new U.S. air base, despite mounting local protests from local citizens and officials.

Local news reports said that the Okinawa regional defense bureau was conducting the survey so as to better understand the depth and density of the seabed's bedrock and the underwater geology and geography of the large area of sea, which will be reclaimed to be used for the U.S. base.

The plan, under a four-year deal between Japan and the United Statesas part of a broader realignment of troops in Japan, will see the construction of a new U.S. marine base and runway on Camp Schwab and a landfill in Oura Bay in Henoko, with the new air base acting as a replacement for the Marine Corps Air Station Futenma, currently located in the densely populated region of Ginowan on the main island of Naha.

But local opposition to the new construction project, which was initially triggered by the defense ministry sinking concrete blocks weighing up to 45 tons into the sea to tether floating "no entry" signs around the drilling zone and in doing so potentially damaging endangered local marine life, is mounting, as Japan's southernmost prefecture hosts the bulk of U.S. military bases in Japan and the locals don't want to see the pristine coastal region of Henoko ruined by another military base.

"This is utterly deplorable. I will use every possible means to realize my campaign pledge of not allowing a base in Henoko," Okinawa Governor Takeshi Onaga, a staunch opponent of the base relocation plan, told a news conference.

The local government, for its part, said it planned to proceed with the drilling and ultimately the base's full construction, but would do so in a manner that would not wipe out marine life in the region, particularly endangered species.

"We will carry on without making a fuss, while making sure the environment around the site will be preserved," said Chief Cabinet Secretary Yoshihide Suga, adding that the relocation plan was the only feasible way of removing the dangers facing locals from the Futenma base, known by many military experts as one of the most dangerous U.S. bases in the world.

Despite the central government's assurances, citizens and local civic groups held a protest outside of the U.S. Marines' Camp Schwab, with some protestors taking small boats to make their feelings heard with megaphones and placards in the waters off Henoko.

Okinawa's officials, including Onaga, have also looked into possibly blocking the construction of a runway planned to be built on reclaimed land in Henoko, under the Japan's Public Water Body Reclamation Law, which states that reclaiming publicly owned water areas requires the approval of the prefectural governor.

If Onaga is successful, the central government will be forced to amend the reclamation law, or change the construction plan, both of which would be a further headache for the central government and likely cause more protests from the islanders.

Prime Minister Shinzo Abehas said he is trying to ease the base hosting burdens of the people of Okinawa as the islanders shoulder the burden of hosting 75 percent of Japan's U.S. bases and around half of all the U.S. military personnel deployed there.

But the tiny island, however, accounts for just one percent of Japan's total land area, and local citizens feel they have suffered for long enough and want the U.S. bases moved off their island entirely.