other infrastructure to accommodate incoming personnel will likely exceed original estimates, Kyodo said, citing diplomatic sources.
Former Prime Minister Yukio Hatoyama had raised the hopes of people on the Japanese southern island of Okinawa last year that the U.S. Futenma airbase could be moved off the island despite a 2006 deal to shift the base to a less crowded part of Okinawa.
But he failed to find a replacement site, sparking public outrage and distracting Washington and Tokyo as the close allies try to cope with an unpredictable North Korea and a rising China.
The planned transfer of about 8,000 Marines to the U.S. territory of Guam from Okinawa by 2014 is part of a larger agreement that includes the relocation of Futenma functions to the less populated area of Okinawa.
Of the total estimated costs of $10.27 billion for the transfer to Guam, Japan was originally set to pay $2.8 billion and extend $3.29 billion in loans, with the remaining $4.18 billion shouldered by the U.S. side.
The additional amount the United States is asking is estimated to come at least to several hundred million dollars, Kyodo said.
The Japanese government, which is facing an urgent task of tackling bulging public debt to stave off the type of sovereign debt crisis that has roiled Greece, plans to reply to the request after an upper house election on July 11, Kyodo said.
