Washington is pressing Japan to take up a bigger share of utility costs at U.S. bases to offset the rising costs of bolstering its military capability in the Asia-Pacific region.

Tokyo has expressed reluctance to accept the demand. A protracted disagreement could damage bilateral ties, especially if coupled with the likely temporary suspension, due to opposition in the divided Diet, of the refueling mission supporting antiterrorism operations and around in Afghanistan.

"A crack could form in the Japan-U.S. relationship," a foreign ministry official said Oct. 7.