Administration officials struggled to explain how President Biden's decision to invoke a Cold War-era statute will help alleviate the shortage of baby formula that has left desperate parents searching for ways to feed their infants.

The Defense Production Act was authorized by Mr. Biden to ensure that formula manufacturers had access to the ingredients and materials they need to ramp up production. Abbott Laboratories, which controls 48 percent of the baby formula market, voluntarily recalled some of its most popular products in February and closed a plant in Michigan due to concerns about possible contamination.

A senior administration official who spoke to reporters on the condition of anonymity declined to say whether any formula companies reported having trouble getting ingredients or materials in a timely manner.

The official repeatedly said that the administration was having active and ongoing conversations with the companies, but wouldn't say what the companies had requested.

The official could not say how fast formula would reach consumers with the invocation of the Defense Production Act. The official wouldn't say why Mr. Biden didn't authorize the use of the law weeks or even months ago.

The official said that the administration had made it clear from the beginning that they were going to pull every lever that they could find.

The act can be used to prioritize raw materials and ensure supply of specialized components, according to a statement from Abbott Laboratories.

We're already express air-freighting infant formula from our F.D.A.-registered facility in Ireland and welcome any support that these added measures can provide in cutting red tape, increasing volume of imports and speeding up transport time from overseas.

The White House has responded to the shortage of baby formula in recent days as media reports about the impact on families have increased. Several small children and infants have been taken to hospitals this week because their parents couldn't find baby formula they needed.

Mr. Biden said in the video that parents were worried about finding enough formula to feed their babies. As a parent and as a grandparent, I know how much stress that can cause.

The FDA relaxed guidelines for imports of baby formula from other countries in order to replenish shelves in the United States. On Wednesday, Mr. Biden announced a plan to use planes contracted by the Defense Department to speed up the import of formula.

The formula would be flown to the companies in the United States, where it would be, according to a second administration official.

The first administration official said that the White House was talking to manufacturers about where there might be cargo around the world that would be suitable for that procedure.

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A growing problem. A nationwide shortage of baby formula has left parents confused and concerned. There are ways to manage uncertainty.

Finding a formula. If your baby's formula wasn't affected by the recall, you can call your local store and ask when it will be back in stock. You can buy it online. If your baby is on special formula, you should reach out to your doctor's office.

A new formula is being picked. If you use a name-brand formula, look for a generic version. If you want a new formula that matches your usual one, seek it. If your baby is on a special formula, make sure to check with your doctor.

A new product transition. You want to switch your child gradually. Gradually phase out the old product when you mix three quarters of your usual formula with one quarter of the new one. If you can transition gradually because you have run out of your usual formula, it's fine.

What not to do. If you can't find your baby's usual formula, don't make your own, homemade formulas are often inadequate and at risk of being contaminated. Don't try to stretch your formula by adding more water, and don't buy it from unvetted online marketplaces. Don't use toddler formula for a baby less than a year old.

The Defense Production Act gave the government the power to ensure the flow of weapons during wartime.

During the coronaviruses epidemic, President Donald J. Trump invoked it as a way of speeding up the production of personal protective gear for hospital workers and the manufacture of vaccines and other drugs. The law was invoked by Mr. Biden to increase domestic production of critical minerals and metals.

Several congressional Democrats praised the president for taking action and said that the administration should do everything they can to resolve the shortages. The administration was criticized for using the act.

The administration has no use for the word defense in the Defense Production Act, according to Senator Patrick J. Toomey. He accused Mr. Biden of using the D.P.A. statute to cover up a product shortage.

The Defense Production Act can cause disruptions to supply chains that ripple across the country, making it a solution that officials often say should be a last resort. Mr. Biden said it was an essential move.

Adequate supply of infant formula is critical to the health and safety of millions of children who depend on the formula for essential nutrition.

The reporting was contributed by Ana Swanson.