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."

White House press secretary Jen Psaki was asked during a press briefing Wednesday whether the postponement of Senate hearings for Biden's pick to manage the Office of Management and Budget was a setback and Psaki said she wouldn't "put it in those terms."

Psaki emphasized that the administration is still "fighting" for Tanden's nomination and remains committed to getting Biden's pick confirmed. When asked whether Tanden had offered to withdraw her nomination, Psaki said that is "not the stage" the administration is in.

"The stage we’re in is working to continue to fight for her nomination. And, as you know, it’s a numbers game, right? It's a matter of getting one Republican to support her nomination," Psaki said. "We're continuing to do that outreach, answer questions they have, and continue to reiterate her qualifications."

The first day of hearings for Biden's pick for secretary of health and human services, Xavier Becerra, kicked off with glowing praise from Democrats, who heralded his experience, and criticism from Republicans, who think his resume is a detractor.

Both Sen. Patty Murray, D-Wash., and Sen. Diane Feinstein, D-Calif., who introduced Becerra, highlighted his potential to make history as the first Latino to lead the department and his experience leading massive departments and in policy as a congressman for 24 years. But Sen. Richard Burr, R-N.C., said he is “not sold” Becerra has the “necessary experience or skills to do this job at this moment.”

Becerra, in his opening statement, said he was committed to working in a bipartisan way.

“No one understands your states and communities better than you. We may not always agree, but if I’m fortunate enough to be confirmed, I will always listen to you and keep an open mind, find common cause, and work with you to improve the health and dignity of the American people,” Becerra said.

Becerra laid out his "vision" for the department with three goals: make COVID-19 treatments more accessible, bring down the cost of health care and restore faith in public institutions by putting science first.

-ABC News' Cheyenne Haslett