The US government is buying 500 million at-home rapid COVID tests that Americans can order online for free starting in January, President Joe Biden says.
He also announced that more testing sites will be set up.
And 1,000 military medical personnel will be deployed as part of efforts to help hospitals overwhelmed by the pandemic.
Around 40 million adults in the US have yet to get their vaccine - as Mr Biden said it was their "patriotic duty".
Addressing the nation on Tuesday, President Biden said: "While COVID-19 has been a tough adversary we have shown we are tougher. Tougher because we have the power of science and vaccines that prevent illness and save lives."
But he warned people who have yet to get the jab: "You have an obligation to yourselves, to your family and quite frankly, I know I will be criticised for this, but to your country.
"I honest to God believe it's your patriotic duty."
And he also pleaded with the "tens of millions" who have been double vaccinated but not yet boosted to come forward.
"I got my booster shot as soon as it was available and just the other day, President Trump announced he had got his booster shot - maybe one of the few things he and I agree on."
Getting vaccinated is "the only responsible thing to do", he said - as he said the US was facing a "critical moment".
President Biden spoke out as a member of his own staff tested positive for the coronavirus, the White House announced on Monday.
The employee spent around 30 minutes on Air Force One while the president was travelling to Philadelphia from South Carolina on Friday, before developing symptoms on Sunday night.
The staff member is fully vaccinated and boosted and tested negative before boarding the jet, White House press secretary Jen Psaki said.
New York and Maine
President Biden (79) is tested regularly and has produced two negative results since Sunday. He will be tested again on Wednesday.
In his speech he said "dozens" of ambulances would be sent to New York and Maine which have seen a surge in cases.
Maine has battling a huge increase in cases in the past fortnight - up from 624 on December 5th to 915 cases on December 19th.
More than 70% of people are said to be vaccinated - but lower rates in rural areas have sparked further outbreaks, officials said.
Maine has recorded more than 137,000 positive cases since the start of the pandemic, together with 1,400 deaths including 22 on Tuesday, according to the Maine Centre for Disease Control and Prevention.
Meanwhile in New York, the Omicron variant has also caused mayhem on Broadway with musicals including 'Aladdin' and 'Hamilton' announcing temporary closures in the face of "extreme uncertainty ahead".
In New York City, around 42,000 tested positive between Wednesday and Saturday - compared with less than 35,800 in all of November.
In Boston, up to 500 members of the National Guard will be deployed to help hospitals battling a surge of COVID-19 patients.
They will be tasked with providing support in key areas including security, transporting patients and delivering food to their rooms.
And in Florida, Omicron has overtaken the Delta variant in Miami-Dade County as the dominant strain, as Mayor Daniella Levine Cava said it was "absolutely astonishing" how contagious the variant has proved to be.
"It's on us to protect ourselves and still the most important thing we can do is vaccinate," she added.
UK restrictions
While in the UK there were 91,743 new COVID-19 cases reported on Monday - the second highest ever - while there were 44 more deaths.
On Tuesday, the country recorded a further 90,629 coronavirus cases and 172 deaths in the latest 24-hour period.
British Prime Minister Boris Johnson has confirmed he will not introduce any further COVID restrictions in England before Christmas, but warned that the situation remains "finely balanced" ahead of the New Year.
In a video posted on social media, he said "people can go ahead with their Christmas plans" but urged caution and suggested people should take a test before meeting elderly relatives.
"The situation remains extremely difficult, but I also recognise that people have been waiting to hear about whether their Christmas plans, your Christmas plans, are going to be affected," Mr Johnson said.
"What I can say tonight is that naturally we can't rule out any further measures after Christmas, and we're going to keep a constant eye on the data - we will do whatever it takes to protect public health."
While Scotland has set strict limits on crowd numbers at football matches.
First Minister Nicola Sturgeon said crowds at outdoor public events will be capped at 500 from December 26th for at least three weeks, while numbers at indoor public events are to be limited to 100 standing or 200 seated.
The restrictions do not apply to private events such as weddings.
Indoor hospitality venues will also return to table service there from December 27th for up to three weeks, and no more than three households will be able to sit in one group.
Ms Sturgeon said the restrictions will be reviewed at the end of the first week of January.
