Under the system, the United States government buys the goods from American agribusinesses, ships them overseas, mostly on American-flagged carriers, and then donates them to the aid groups as an indirect form of financing. The groups sell the products on the market in poor countries and use the money to finance their antipoverty programs. It amounts to about $180 million a year.

Neither the Bush administration nor members of Congress are looking to undo the practice, which has gone on for more than a decade. In fact, some of the nonprofit groups say it has worked well and are pressing for sharp increases in the amount of American food shipped for sale and distribution to support development programs.

The Christian charity World Vision and 14 other groups, which call themselves the Alliance for Food Aid, say that CARE is mistaken; they say the system works because it keeps hard currency in poor countries, can help prevent food price spikes in those countries and does not hurt their farmers. Not least, they argue, it also pays for their antipoverty programs.

But some people active in trying to help Africa’s farmers are critical of the practice. Former President Jimmy Carter, whose Atlanta-based Carter Center uses private money to help African farmers be more productive, said in an interview that it was a flawed system that had survived partly because the charities that received money from it defended it.

Agribusiness and shipping interest groups have tremendous political influence, but charitable groups are influential, too, Mr. Carter said, because “they speak from the standpoint of angels.”