(a) The Regional Administrator may provide up to 75 percent of the approved work plan costs.

(b) The Regional Administrator may increase the maximum federal share if the Tribe or Intertribal Consortium can demonstrate in writing to the satisfaction of the Regional Administrator that fiscal circumstances within the Tribe or Consortium are constrained to such an extent that fulfilling the match requirement would impose undue hardship, except that the federal share shall not be greater than 90 percent.