The Biden administration is planning to send states, pharmacies and community health centers 3 million to 4 million doses of Johnson & Johnson's coronavirus vaccine as early as next week, a White House official said Wednesday.

White House COVID-19 response coordinator Jeff Zients told reporters that if the vaccine is authorized by the Food and Drug Administration (FDA) this weekend, "we are ready to roll out this vaccine without delay."

That 3 million to 4 million number is an increase over what officials told governors on Tuesday, and likely reflects the fact that Johnson & Johnson told Congress it will have 4 million doses ready to ship immediately upon authorization.

Johnson & Johnson said it aims to deliver a total of 20 million doses by the end of March, and 100 million doses by the end of June. Zients said the administration is working with the company to "accelerate the pace and time frame" for the full 100 million doses.

An FDA advisory committee is scheduled to meet on Friday to recommend giving the green light to the Johnson & Johnson vaccine based on its safety and effectiveness.

An agency analysis published Wednesday ahead of the meeting shows the single shot vaccine is effective at preventing most cases of moderate and severe disease.

The Johnson & Johnson shot could ease the complicated logistics of the U.S. vaccine rollout. Unlike the vaccines from Moderna and Pfizer, Johnson & Johnson's shot can be stored in a normal refrigerator for several months, rather than at ultra-cold temperatures.

And as a single shot, there won't be a concern about scheduling or having enough supplies for a second dose.