After an expanded detention facility for child migrants reopened in Carrizo Springs, Texas, Rep. Alexandria Ocasio-Cortez, D-N.Y., tweeted Tuesday, “This is not okay, never has been okay, never will be okay - no matter the administration or party.”

In a press briefing Wednesday, Psaki attempted to cast the Biden administration’s efforts to manage immigration as a major improvement over President Donald Trump’s policies but didn’t fully address Ocasio-Cortez's criticism that such facilities shouldn’t exist at all.

Psaki said the administration had three options when it comes to child migrants: to send them back to their countries (which she said can be dangerous), to transfer them to a facility managed by the Department of Health and Human Services, or to put them in the care of families or sponsors "without any vetting." She said the administration has chosen the middle option.

“What we are doing is working as quickly as possible to process these kids into these HHS facilities, which have been revamped, which have medical and educational services available, so that we can then transfer them to families. That's what our approach is,” Psaki said.

Psaki would not commit to a request to allow media in to prove that children are treated humanely, citing privacy and security concerns. Psaki tried to explain the administration’s options in dealing with minors at the border and why the detention facilities have become a primary strategy.

“This is a difficult situation. It's a difficult choice. That's the choice we've made,” she said.

Psaki also attempted to defend delays in transferring children from facilities run by Customs and Border Protection, which often lack amenities, to Health and Human Service facilities that are intended for longer-term care. By law, children are supposed to spend no more than 72 hours in Customs and Border Protection facilities after initial apprehension.

“There were some delays last week because of weather, and because some of these facilities to safely move these kids to, did not have power and were not in a place where they could -- they had the capacity to take in these kids and do it safely. That is not our objective. That is not our goal," Psaki said. "So some, unfortunately, did stay four days, five days, or longer, but the objective is to move them as quickly as possible to the HHS sponsored facilities.”

-ABC News' Sarah Kolinovsky

In keeping with the White House's focus of the day, Biden held a bipartisan Oval Office meeting Wednesday with House and Senate members ahead of signing an executive order mandating a review of critical U.S. supply chains.

"The last year has shown the vulnerability we have with some of the supply chains, including the PPE that we needed badly but had to go abroad to get. And there are current strategies," Biden said.

Biden praised the bipartisan effort to address the shortage of the chips for cars and said the group planned to discuss the problem, along with other shortage issues.

-ABC News' Molly Nagle

The White House was surprised to discover that Johnson & Johnson will only have about 3 to 4 million doses of its vaccine ready to ship once the FDA grants an emergency use authorization, White House press secretary Jen Psaki said during a press briefing Wednesday.

Johnson & Johnson had estimated it could ship 12 million doses at the end of February in a $1 billion contract signed with the federal government in August.

“We were surprised to learn that Johnson & Johnson was behind on their manufacturing. As you noted, it was kind of reported earlier to be about 10 million, and now it's more like 3 to 4 million doses that they would be ready to ship next week if they are moved through the FDA process, which is not yet concluded, just to note," Psaki said. "And we are going to continue to work with them on ensuring that that can be expedited.”

Despite the initial availability, Johnson & Johnson has said it expects 20 million doses to be available by the end of March and to meet its contractual obligation for 100 million doses by the end of June.

-ABC News' Sarah Kolinovsky

Veteran diplomat Linda Thomas-Greenfield was sworn in Wednesday morning as Biden's U.N. ambassador. Thomas-Greenfield, known for her "gumbo diplomacy", is a Louisiana native and child of the segregated South.

After being sworn in, Thomas-Greenfield tweeted saying she was "honored" to hold the post.

"Diplomacy is back. Multilateralism is back," Thomas-Greenfield said in the tweet. "America is back."

Biden and Harris will participate in an event Thursday afternoon commemorating 50 million COVID-19 vaccine shots administered during the Biden administration, which is halfway to Biden’s goal of distributing 100 million COVID-19 shots in his first 100 days in office.

When Biden set out the goal at the beginning of his term, the administration was already on pace to administer nearly 1 million vaccines a day, which some public health experts have said is not fast enough to control the pandemic.

Dr. Anthony Fauci, Biden’s chief medical adviser, has estimated that 325 million people will need to be immunized for the pandemic to end and to reach that threshold, Biden would need more vaccinations.

Biden has rejected the suggestion that his goal was too low, telling reporters in January that, "it's a good start."

Meanwhile, Harris visited a Giant supermarket in Southeast Washington, D.C. Thursday morning to promote the administration’s Federal Retail Pharmacy Program for COVID-19 vaccinations, which has delivered 1 million doses to over 6,500 pharmacies across the country.

Harris spoke to the store's pharmacist and then watched as a patient, Brenda Thompson, received her second dose of the Moderna vaccine.

Biden will also participate in the National Governors Association’s Winter Meeting Wednesday afternoon, and the White House will give a press briefing at 12:30 p.m.