The United States has told Japan it plans to reduce the number of troops in Okinawa Prefecture as part of a major military realignment, but the proposal's feasibility remains unclear due to local opposition in other parts of Japan.

Japanese sources said strong opposition from local officials in places where Washington wants to transfer the troops has left Tokyo cautious, and negotiations over the realignment are likely to be prolonged.

"I haven't got a clue how much of that can be realized," a government source said. "(The negotiations) have just begun."

At working level talks that began Thursday, the U.S. and Japan discussed moving some marines in Okinawa to Camp Fuji in Shizuoka Prefecture.