Two Japanese prefectures said they have started collecting optional $10 fees from Mount Fuji climbers and the fees may become mandatory next year.

Yamanashi and Shizuoka prefectures said many climbers have been handing the $10 optional payments to officials holding signs reading, "Convey your feelings to Mount Fuji," as part of a scheme to raise money for preservation efforts at Mount Fuji -- which was recently named a U.N. Educational, Scientific and Cultural Organization world heritage site -- Kyodo news reported Thursday.

"I paid the entrance fee because I wanted to give my support to the project," said Mieko Yamada, 65, who climbed the Yoshida trail Thursday. "I hope the money will be used for environmental preservation."

Officials said the optional fee, part of the Cooperative Fund for Environmental Conservation of Mount Fuji, is being accompanied by questions about whether climbers would accept the fee becoming mandatory next year.