Japan's plan to send Self-Defense Forces personnel to a U.S. Marine base in Okinawa following several helicopter mishaps in the region earlier this year has hit a snag due to U.S. reluctance, a Japanese government source said Saturday.

The move involving U.S. Marine Corps Air Station Futenma was aimed at allaying safety concerns fanned by a spate of emergency landings involving U.S. military helicopters since January, the source said.

But a senior Defense Ministry official said they have not heard from the U.S. side since receiving a request to postpone the plan, indicating talks to proceed with the deployment are proving difficult.