Several hundred people rallied against a contentious plan to relocate a U.S. military base to another site on Okinawa ahead of U.S. Ambassador Caroline Kennedy's visit to the southern Japanese island.

Kennedy was to arrive later Tuesday in Okinawa, home to about half of 50,000 U.S. troops based in Japan under bilateral defense pact. She is to meet with Okinawan officials and reportedly see the base relocation site during her three-day visit.

Opponents want the base moved off Okinawa completely.

Okinawa's governor signed off on the long-overdue relocation of the Futenma air base in December, a major step to allow the U.S. to pursue its troop realignment. It also paves the way for Tokyo to move the base to a coastal area in a less crowded part of the island.