State and local officials are scrambling to figure out how to feed about 335,000 Iowans who face the loss of millions of dollars in food assistance as the federal government shutdown enters a fourth week on Saturday.

The Iowa Department of Human Services says it's working on contingency plans, but officials could offer no details about what's being considered to cover all or part of the $38 million Iowans receive monthly through the supplemental nutrition assistance program, or SNAP, if federal funding stops.

U.S. Agriculture Secretary Sonny Perdue said Tuesday his agency had found a way to ensure residents get benefits through February, but had no immediate plan for providing assistance in March.

Perdue said he hopes Congress will send a spending bill that President Donald Trump can sign. Trump's fight with lawmakers for nearly $6 billion in funding for a border wall with Mexico has resulted in a shut down of all but essential services.

Tara Nall said she doesn't know what she'll do to feed her family if she loses all or part of the $500 she receives monthly for food.

The Des Moines mom of two works a few hours in a part-time job, but it doesn't give her much income to buy groceries.

"I'll make it work. I don't know how, but I'll make it work," said Nall, who expects to look to food banks for help.

Advocates for Iowa's poor say it will be impossible for food banks to make up for the loss.

"We'll have a major crisis at home, in Iowa, if people aren't able to purchase food," said Anne Bacon, executive director for Impact Community Action Partnership, a Des Moines group that helps low-income families.

Iowa's "most vulnerable families" will face "extraordinarily challenging choices," she said.

"If families have to choose between buying food or paying a bill, they'll buy food. And that creates a cascade of problems: rent that's not paid, car payments that aren't made," potentially hurting their ability to work, Bacon said.

Food assistance funded through February

With $3 billion in reserve, the U.S. Department of Agriculture has about 60 percent of the $4.8 billion needed to provide food assistance to about 19 million American families in March, according to estimates from the Center for Budget Policy and Priorities, a Washington, D.C., research institute.

If that's the course USDA uses, it would mean at least a 40 percent reduction in benefits for food assistance — commonly known as food stamps.

States could choose to help supplement aid, if they have the money, but could run into operational challenges, such whether they'll be able to load electronic benefit cards if the program is shut down, said Dottie Rosenbaum, a senior fellow at the center.

Iowa DHS said it's drafting contingency plans should they be needed. Gov. Kim Reynolds, a Republican, told reporters this week the state would reassess the need for services if the shutdown continues.

Food banks are bracing for a possible onslaught of demand.

'We don't know what it would look like'

Even though previous shutdowns have threatened assistance, the federal government has never stopped providing food to needy families. Local leaders hope this time isn't an exception.

"It would be unprecedented," said Luke Elzinga, communications and advocacy manager at the Des Moines Area Religious Council, which runs a food pantry network in the metro area.

A small decline in food assistance benefits in 2013 — an average decline of $18 per household — pushed demand at area food banks up 20 percent, Elzinga said.

"It would be such a big impact, we don't know what it would look like," he said.

In Polk County, around 60,000 residents receive about $7 million in federal food assistance monthly.

If all those families came to the food bank, it would nearly triple the highest number of people the pantries have ever served in a month, Elzinga said.

DMARC has no plans to turn anyone away, providing at least a three-day supply of healthy groceries, even if that means dipping into the group's reserves and sending out pleas for emergency donations, he said.

"If we're talking about families losing a good portion of their SNAP benefits, a three-day supply isn't going to be enough," Elzinga said.

"Even under the current benefits, three days aren't enough," he said.

Shutdown becomes longest in U.S. history

Even with mounting political pressure to reopen the federal government, it's unclear how long the shutdown will last, said Donna Hoffman, a University of Northern Iowa political science professor.

"This one is fairly unique since it essentially started under a unified government," Hoffman said.

Republicans controlled the House, Senate and White House in December, when leaders failed to reach an agreement over the border wall. Democrats have since taken control of the House.

The partial shutdown, which began Dec. 22, officially becomes the longest in U.S. history on Saturday.

"When people stop getting paychecks, when people stop getting SNAP and other benefits, the pressure will mount ... on members of Congress" to reach an agreement, Hoffman said. "But it's anyone's guess when this will end."

Bacon, director of Impact Community Action Partnership, said low-income families have little money to fall back on if food or other assistance disappears.

Advocates say vouchers for low-income housing also are slated to end in March.

"Even in the best of economic times, these families are … the first ones to get hurt," Bacon said.

God 'hasn't let us down yet'

In Iowa, about 70 percent of families receiving food assistance have children. The remainder of recipients are either elderly or have a disabled family member. About half the families work, data from Child & Family Policy Center in Des Moines show.

Despite the low unemployment rate, Elzinga said the Des Moines Religious Council's pantries served a record number of people last year. Families struggled with mostly stagnant wages failing to keep up with higher costs for rent, child and health care.

Families supplemented their groceries with the pantries' "anytime items" — a mix of dried beans and short-shelf items such as rice, baked goods and produce — that are made available daily until they're gone.

"We have more people using the food pantries more often," he said.

Nall, the Des Moines mother of two, said she's already careful to make her food budget stretch, even if she and her daughters have to rely on hot dogs and Ramen noodles.

The 36-year-old, who is training for what she hopes will be a higher paying job, said she's faced uncertainties before. "I have a strong faith in God and he hasn’t let us down yet," she said.