The two sides agreed last October on a sweeping plan to reorganise U S military personnel in Japan, who number some 50,000. It would shift 7,000 Marines from Japan's southern island of Okinawa to the U S territory of Guam, among other things.
The plan is part of Washington's global strategy to make its forces more flexible. Another stated goal in Japan is to reduce tensions with communities that host U S bases, but the scheme has run afoul of local residents concerned about noise, accidents and crime associated with the American troops.
Talks earlier this week between Japanese defence officials and the mayor of Nago City on the southern Japanese island of Okinawa failed to narrow differences over the proposed relocation of the U S Marines' Futenma air base from a crowded part of the island to an area straddling another base and the Nago coast.
The United States has offered to increase the number of Marines to be moved to Guam to 8,000, but relocating Futenma is a a prerequisite and vital to the overall realignment deal.
U.S. and Japanese negotiators will also be discussing how much of the bill for the base reorganisation Japan should foot.
Washington has proposed that Tokyo pay 75 percent of the estimated billion it will cost to move the Marines to Guam, while Japan wants to provide at least some of the funds in the form of loans because of its huge public debt.
''It's not that easy,'' said one Japanese government source about the discussions on funding.
Resentment of the U S military runs deep in Okinawa, one of Japan's poorest areas and the reluctant host to almost half the American forces in the country, including nearly 12,000 Marines.
But resistance is also strong elsewhere.
Earlier this month, voters in the western Japanese city of Iwakuni gave a thumbs down to a plan to expand a U S Marine base there in a rare, but non-binding, referendum.
REUTERS SK KP0937