Joe Biden's goal of seeing 100 million doses of coronavirus vaccine injected within his first 100 days in office is "absolutely" achievable, top US scientist Anthony Fauci said Sunday, days before he is to become the new president's chief advisor on Covid-19.

"The feasibility of his goal is absolutely clear, there's no doubt about it," Fauci, the best-known face of the government's fight against the deadly virus, told NBC's "Meet the Press."

"That can be done," said Fauci, an infectious disease specialist who also has advised President Donald Trump.

While US health authorities succeeded in testing and confirming the safety and effectiveness of two new vaccines in record time, an ambitious effort to quickly inoculate millions of Americans has fallen short, drawing widespread criticism.

According to the federal Centers of Disease Control (CDC), 31.1 million doses have been delivered so far, but less than 40 percent (12.2 million) has been administered.

In early December, administration officials were predicting 20 million people would receive a first dose of the two-dose regimen by the end of that month.

Some states, including New York, have warned that they may exhaust their vaccine supplies as early as the coming week due to a shortfall in deliveries coordinated by the federal government.

That comes as the states were attempting to accelerate the pace of vaccinations.

The country is currently facing the worst coronavirus surge yet. On Tuesday, a grim new record was set as the disease claimed 4,470 lives in 24 hours. The latest five-day count is close to 20,000.

Biden's future chief of staff Ron Klain said Sunday that the overall death count, now more than 396,000, could surpass 500,000 in February.

"The virus is going to get worse before it gets better," he told CNN. "It's going to take a while to turn this around."

Klain said that to accomplish its goal for accelerated vaccinations, the Biden administration could invoke the Defense Production Act, which allows the government to require companies to produce items deemed necessary in an emergency.

The future president also has said he will mobilize the National Guard as well as the Federal Emergency Management Agency to help set up additional vaccination centers.