Michelle Obama is extending her campaign against childhood obesity by urging women to breastfeed and calling for the removal of barriers to nursing at work.
The Obama administration has already introduced more flexible work rules and tax breaks on nursing equipment in order to encourage American women to breastfeed.
A recent study published in the journal Pediatrics found that babies who were breastfed for the first four to six months were less likely to be overweight or obese than children who were fed using formula and began eating solid foods before their fourth month.
The move risks fresh controversy for Mrs Obama after she was accused by Sarah Palin, the former Alaska governor, and others of trying to use government power to dictate private behaviour like eating habits.
Giselle Bundchen, a famous model, created a furore last year when she declared: "There should be a worldwide law, in my opinion, that mothers should breastfeed their babies for six months."
About three-quarters of American mothers breastfeed less than that in developing countries.
"Breastfeeding is a very personal choice for every woman," Kristina Schake, Mrs Obama's communications chief, told Politics Daily. "We are trying to make it easier for those who choose to do it."
Discussing her "Let's Move" anti-childhood obesity campaign, Mrs Obama said she wanted "to focus on the important touch points" in a child's life. "And what we're learning now is that early intervention is key. Breastfeeding. Kids who are breastfed longer have a lower tendency to be obese."
Mrs Obama has previously spoken about going to a job interview when she was breastfeeding her younger daughter Sasha, now eight. "I packed up that little infant, and I put her in the stroller, and I brought her with me. And I prayed that her presence wouldn't be an automatic disqualifier.
"And it was fortunate for me that, number one, she slept through the entire interview. And I was still breastfeeding – if that's not too much information. And I got the job."
The White House is sensitive to accusations that Mrs Obama is dictating what women should do. Robin Schepper, director of "Let's Move" insisted to "Politics Daily" that the First Lady "is not telling women to breastfeed".
Valerie Jarrett, a senior White House adviser, wrote in an official blog: "One of the most common reasons mothers cite for discontinuing breastfeeding is returning to work and not having break time or a private space to express milk."
Mrs Obama drew attention last September to the problems of obesity and low breastfeeding rates among black Americans.
She said: "We're also working to promote breastfeeding, especially in the black community, where 40pc of our babies never get breastfed at all, even in the first weeks of life, and we know that babies that are breastfed are less likely to be obese as children."