TOKYO (Kyodo) -- The transfer of U.S. Marine Corps troops from Okinawa to Guam has begun, under an agreement reached more than a decade ago as part of efforts to reduce the base-hosting burden on local communities in Japan's southern island prefecture, the Japanese Defense Ministry said Saturday.

Some 100 logistics personnel will be relocated to Guam through 2025, as the first of the over 4,000 members of the Corps to be transferred. Some 5,000 more are also expected to move out of Japan, to locations such as Hawaii, but the timeline for the completion is unclear.

"A major milestone has been reached since the relocation of the U.S. Marines in Okinawa to Guam was stipulated in the U.S.-Japan Roadmap for Realignment Implementation in May 2006," the Japanese Defense Ministry said in a statement.

The U.S. military, meanwhile, said the U.S. and Japanese governments will "continue to work together to strengthen deterrence and response capabilities of the U.S.-Japan alliance, while mitigating the impact on local communities, including those in Okinawa."

The alliance's response capabilities will be strengthened by Marines and the Japan Self-Defense Forces conducting joint training in Guam and the nearby Northern Mariana Islands, it said.

Due to the legacy of the U.S. occupation after World War II and Okinawa's strategic importance, owing to its relative proximity to China and the Korean Peninsula, Okinawa has hosted the bulk of U.S. military facilities in Japan and its residents have for decades bristled at crime and pollution linked to the military presence.

Under the Japan-U.S. forces realignment road map agreed in 2006, the transfer of the Marines to Guam was interconnected with the centerpiece plan to move the U.S. Marine Corps' Futenma Air Station from the residential district of Ginowan to the less densely populated Henoko coastal area in Nago within Okinawa.

But Japan and the United States agreed in 2012 to "delink" the Futenma relocation plan with the Guam transfer plan amid slow progress on the Futenma project, with locals calling for the base to be moved out of Okinawa.

They agreed at that time on the relocation of approximately 9,000 Marine Corps from Okinawa to locations outside of Japan. This would lead the total number of Marines stationed on the island prefecture to drop to around 10,000.

The 4,000 service members set to move to Guam will mainly come from the 3rd Marine Expeditionary Brigade at Camp Courtney, the 4th Marine Regiment at Camp Schwab and the Combat Logistics Battalion 4 at Camp Foster, according to the Japanese ministry.

Japanese Defense Minister Gen Nakatani conveyed the commencement of the Marines' transfer to Nago Mayor Taketoyo Toguchi on Saturday.

Toguchi, speaking to reporters, welcomed the development as it is expected to alleviate the local burden. But some residents complained at the small number of the initial relocation.

"Unless the U.S. military is gone, crimes will not be eradicated. I do not feel safe with only 100 troops moving out," said Kikuko Nakahara, 64, who was protesting against the landfill work for the relocation site for the Futenma base, apparently referring to sexual assault cases involving U.S. servicemen.

It remains to be seen to what extent locals will feel a reduction in their burden, with the central government also beefing up Japan's defense posture amid China's growing military assertiveness in the region.

A Japanese Defense Ministry official did not reveal when the relocation of the subsequent batches of personnel will take place, saying, "The Marine Corps has not made a decision on its plan."

The cost of the transfer to Guam is estimated at around $8.6 billion, the ministry said.

The Japanese government will shoulder up to $2.8 billion to support infrastructure projects on Marine Corps Base Camp Blaz, the relocation site for the Marines from Okinawa, and other U.S. military facilities, according to the U.S. forces.

Okinawa Prefecture hosts over 70 percent of facilities exclusively used by the U.S. military despite accounting for only 0.6 percent of Japan's total land area.