States including Michigan, New Jersey, New York, Oregon, South Carolina and Vermont have shown signs of vaccine supply strain and are asking for more doses of both approved vaccines, one from Pfizer-BioNTech and the other from Moderna.
The number of deaths has spiked since Christmas.
During the past three weeks, US coronavirus fatalities have totalled 63,793 compared with 52,715 deaths in the three weeks prior to Christmas, an increase of 21%, according to a Reuters analysis.
The daily COVID-19 death numbers crossed 4,000 for the first time on Jan. 6.
Eighteen US states, including California, Pennsylvania, Texas and Washington reported their highest daily death numbers in January, according to the Reuters tally.
The number of coronavirus cases has risen across all US regions and on Tuesday crossed 24 million since the pandemic started.
While seriously ill patients are straining healthcare systems in parts of the country, especially in California, the national rate of hospitalisations has levelled off in the past two weeks and was near 124,000 on Tuesday.
President-elect Joe Biden, due to be sworn in on Wednesday, has proposed a $1.9 trillion aid package that includes $415 billion to bolster the response to the virus and the rollout of COVID-19 vaccines, some $1 trillion in direct relief to households, and roughly $440 billion for small businesses and communities hardest hit by the pandemic.