The US public will start receiving the Pfizer/BioNTech coronavirus vaccine from Monday after it was authorised for emergency use, officials say.
The first three million doses of the vaccine would be shipped "across all states" this weekend, said Gen Gustave Perna, who is overseeing distribution.
The vaccine offers up to 95% protection against Covid-19 and was deemed safe by the Food and Drug Administration (FDA).
On Saturday, the US recorded a daily toll of 3,309 Covid-related deaths.
The figure, reported on the Johns Hopkins University website, is the highest total in a single day anywhere in the world.
Coronavirus deaths have been rising sharply since November in the US, reports BBC.
Authorising the emergency use of the Pfizer/BioNTech vaccine on Friday, the FDA - which had come under intense pressure from the Trump administration to do so - said the move was a "significant milestone" in the pandemic.
A mass inoculation drive using doses of the same vaccine has already begun in the UK.
During a news conference on Saturday, Gen Perna - speaking for the US government's vaccination campaign Operation Warp Speed - said doses of the vaccine would be packed into shipping containers for transportation "within the next 24 hours".
"Expect 145 sites across the states to receive the vaccine on Monday, another 425 sites on Tuesday, and the final 66 sites on Wednesday," he said, adding that next week's distribution would complete the initial delivery of the Pfizer/BioNTech vaccine and cover about three million people.
Gen Perna told reporters he was "100% confident" that the doses "needed to defeat the enemy Covid" would be transported safely.
He warned, however, that while it had been a week of progress, "we are not done until every American has access to a vaccine".
What has the FDA said about the vaccine?
"The FDA's authorisation for emergency use of the first Covid-19 vaccine is a significant milestone in battling this devastating pandemic that has affected so many families in the United States and around the world," the head of the agency, Stephen Hahn, said.
He said the authorisation came after "an open and transparent review process" that ensured the vaccine met the "FDA's rigorous, scientific standards for safety, effectiveness, and manufacturing quality".
On Thursday, medical experts advising the FDA recommended the emergency-use authorisation. A 23-member panel concluded the vaccine's benefits outweighed its risks.
Emergency use, the FDA said, was not the same as full approval, which would require Pfizer to file a separate application to secure.
US media reported that Mr Hahn had earlier been told to approve the vaccine for emergency use by Friday or quit.
Mr Hahn, however, said the reports were "untrue" and stressed that the agency had not compromised safety in its testing.