The construction began despite protests and opposition from the locals, some of whom clashed with police as the construction work went on. The locals don't want the base relocated to another part of the island, but rather, moved off the island completely.

The American air base in Okinawa has been a controversial issue locally, especially because it is surrounded by civilian facilities like schools, hospitals, and residential homes. The Japanese government froze the relocation of the base in August in order to consult more with the locals and with Washington.

The Okinawa Airbase is home to 28,000 American troops, USA Today reported. American troops have been in Japan since 1945, when Japan was invaded during World War II.

While the locals have often complained of the inconveniences of the airbase - from loud noises of aircraft landing and taking off, to accusing U.S. Marines of misconduct at times - the government is keen to maintain the Americans' presence in the wake of a belligerent, rising China.

An alternative base is to be built in Henoko, which authorities say is less populated, according to the Japan Times.

Defense Minister Gen Nakatani, while briefing reporters on Thursday, said that the relocation of the base would "remove anxiety of people living near the (Futenma) air base and eliminate the noise pollution and risks."

Japanese president Shinzo Abe recently visited Washington, where both countries reaffirmed their commitment to work together in security and defense cooperation, among other areas.