The Baltic Dry index, which tracks changes in the price of shipping commodities, has been on the decline for the past 14 sessions amid fears of a global economic slowdown.
Until the 1970s it was the principal port of Guatemala, used primarily for shipping agricultural commodities.
"It seemed counterproductive to ship in commodities and undermine local producers," said Gawain Kripke, director of policy for Oxfam America.
The food aid budget should not be a backdoor subsidy for domestic producers; and even under the new approach, 55 percent of food aid dollars would still be used to purchase and ship American commodities.
On a tour of South America last November, China's president, Hu Jintao, expressed his intent to put money into the region's infrastructure, the better to ship its commodities out.
The price of shipping important commodities like coal, iron ore and grain has dropped sharply over the last three weeks, though it still remains high by traditional measures, according to the Baltic Exchange Dry Index, a much-watched gauge of shipping prices that is seen as an indicator of global demand.
In response, the administration urged Congress to give it more flexibility to buy food for donation from local and regional providers, a method that antihunger experts say is cheaper and more efficient than buying and shipping American commodities, as well as encouraging agricultural development.
He also argues that the findings show that rather than shipping single commodities, Greek merchants were trading in "value added" items, the ancient Greek version of the prepared-food aisle in the supermarket.
Fruits and vegetables are now being grown, packaged and shipped like industrial commodities.
The main commodities shipped are grain from Thunder Bay on Lake Superior to St. Lawrence ports, and iron ore to steel mills in both Canada and the United States.
Commodities shipped by barge have a low profit margin, and extra transportation costs would probably make them unsellable, Mr. Biel said.
