MANCHESTER, New Hampshire: Food banks around the country are reporting critical shortages that have forced them to ration supplies, distribute staples usually reserved for disaster relief and in some instances close.

"It's one of the most demanding years I've seen in my 30 years" in the field, said Catherine D'Amato, president and chief executive of the Greater Boston Food Bank, comparing the situation to the recession of the late 1970s.

Experts attributed the shortages to an unusual combination of factors, including rising demand, a sharp drop in U.S. supplies of excess farm products, and tighter inventory controls that are leaving supermarkets and other retailers with less food to donate.

"We don't have nearly what people need, and that's all there is to it," said Greg Bryant, director of the food pantry in Sheffield, Vermont

"We're one step from running out," Bryant said.

"It kind of spirals," he added. "The people that normally donate to us have less, the retailers are selling to discount stores because people are shopping in those places, and now we have less food and more people. It's a double, triple, hit."

The Vermont Food Bank said its supply of food was down 50 percent from last year. "It's a crisis mode," said Doug O'Brien, the bank's chief executive.

For two weeks this month, the New Hampshire Food Bank distributed supplies reserved for emergency relief. Demand for food here is up 40 percent over last year and supply is down 30 percent, which is striking in the state with the lowest reliance on food banks.

"It's the price of oil, gas, rents and foreclosures," said Melanie Gosselin, executive director of the New Hampshire Food Bank.

Gosselin said household budget squeezes had led to a drop in donations and greater demand. "This is not the old 'only the homeless are hungry,'" she said. "It's working people."

Lane Kenworthy, a professor of sociology and political science at the University of Arizona, agreed, saying: "The overall picture is that household incomes are kind of stuck. There's very little way to increase income, and most people have a very heavy debt load. Any event that increases your costs is really, really troublesome, because you're already stretched thin."

The food bank in Manchester delivers provisions to a housing project each week, and on a recent Monday, Matthew Whooley, 26, of Manchester, was waiting in line with his wife, Penny, and their four children.

"Every week there's less and less food," Whooley said. "It used to be potatoes, meat and bread, and last week we got Doritos and flour. The food is getting shorter, and the lines keep getting longer."

In part, food banks are suffering because farmers are doing well. The food banks rely on supplies from the U.S. Agriculture Department's Bonus Commodity Program, which buys surplus crops like apples and potatoes from farmers.

"Right now, the agricultural economy is very strong and the surpluses aren't available for us to purchase," said Jean Daniel, a department spokeswoman. "Certainly we're empathetic, but unfortunately we cannot count on those bonus commodities every year."

Supplies from the surplus program dropped to $67 million worth last year, from $154.3 million in 2005 and $233 million in 2004. Figures for this year are not available, Daniel said.

Food bank operators are lobbying for passage of a farm bill currently stalled in the Senate that would raise emergency aid for food banks to $250 million a year, from $140 million. That figure has remained steady since 2002.

Susannah Morgan, executive director of the Food Bank of Alaska said, "The biggest problem is that the federal government's programs are dropping as need is growing."

Morgan said the decline has affected rural Alaska, where native tribes run most food pantries. She said about 10 percent of the state's rural food banks have closed because there is not enough federal help coming in.

"They don't feel staffing and heating is worth it for the small amount of food," Morgan said.

Further complicating the picture, Morgan and others said, is tighter inventory monitoring, which has left many stores with less to donate.

"They know exactly what they have, down to the can," said Darren Hoffman, a spokesman for the Los Angeles Regional Food Bank, whose supplies are down 11 percent this year. "They can track a lot better and don't order in bulk. Efficiency has kind of been the enemy of the food bank."

Extra food — items that are not selling or seasonal inventory that is no longer needed — is now often sold to low-cost retailers, said Tim Viall, executive director of the Greater Stockton Food Bank in Stockton, California

"We're getting fewer canned goods than last year from retail grocers, because they're selling it to warehouse food stores," Viall said. "We're putting more reliance on canned food drives, and we're trying to ramp up the fresh fruit and produce. We are in the heart of one of the most productive agriculture areas in the world, and we're trying to take advantage." In places where community donations are down and there are no food manufacturers to solicit, pantries and food banks are making difficult choices. The Society of St. Vincent de Paul food pantry in Cincinnati is giving families less food this year because there is not enough. It has started to ask smaller families to take fewer products.

"Donations are down, and people who need help is up," said Liz Carter, executive director of the food bank. "So what are we going to do. We just made the decision that instead of giving people six or seven days worth of food, we're going to give them three or four days of food, which is a drop in the bucket."

Ginny Hildebrand, executive director of the Association of Arizona Food Banks, said many pantries were facing similar situations.

At a recent conference for food bank employees, Hildebrand said, "Everybody was saying the same thing. They're all hit by an increase in demand, all hit by the impact of the higher costs of food, and all hit by federal reductions. We just don't have the quantity of products available that we used to."

Ross Fraser, a spokesman for America's Second Harvest, which distributes more than two billion pounds of donated food and grocery products annually, said the shortages at food banks were the worst the organization had seen in 26 years.

"Suddenly it's on everyone's radar," Fraser said. "Food banks are calling us and saying, 'My God, we have to get food.'"