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."

National Economic Council Deputy Director Sameera Fazili and National Security Council Senior Director of International Economics and Competitiveness Peter Harrell joined a White House press briefing to discuss the executive order Biden will sign Wednesday afternoon that will commence an investigation and deliver recommendations to fix supply chain vulnerabilities revealed by the COVID-19 pandemic.

"Make no mistake, we are not simply planning to order up reports. We are going to be taking actions to close gaps as we identify them..." Harrell said.

The executive order will mandate a 100-day review of critical product supply chains in the U.S. focused on those for computer chips, large capacity batteries, active pharmaceutical ingredients and critical minerals and strategic materials, including rare earth minerals.

Fazili argued the investigation could be good for the U.S. economy.

"There are opportunities for small business development to help diversify supplier networks and alleviate the risk of too-big-to-fail companies in the supply chains for critical goods," Fazili said. "There are opportunities to improve worker readiness and training so they have the skills needed to ramp up research, production, or distribution of a critical good."