With the budget deficit growing and President Bush promising to reduce spending, the administration has told representatives of several charities that it was unable to honor some earlier promises and would have money to pay for food only in emergency crises like that in Darfur, in western Sudan. The cutbacks, estimated by some charities at up to $100 million, come at a time when the number of hungry in the world is rising for the first time in years and all food programs are being stretched.