The United States reported more than one million new Covid-19 cases Monday after the long New Year's weekend, according to data from Johns Hopkins University, as the Omicron variant spread at a blistering pace.

There were 1,080,211 new cases in the country, a global record, although the number of cases reported on a Monday is usually higher than other days because of delays in weekend tallying, especially after such a three-day holiday weekend.

Still, the figure is double the number of daily cases compared to the previous Monday.

The rolling average over seven days -- which experts see as more reliable -- was 486,000 cases per day as of Monday evening, the university said.

The new figure comes a day after top US pandemic advisor Anthony Fauci said the country was experiencing "almost a vertical increase" in Covid-19 cases, adding the peak may be only weeks away.

The heavily mutated Omicron strain -- the most transmissible to date -- accounted for around 59 percent of US cases in the week ending December 25, according to government modeling.

Fauci said the experience of South Africa -- where the strain was first detected in late November and peaked quickly, then subsided nearly as speedily -- offered some hope.

Rates of death and hospitalization in the United States have been lower in recent weeks than during previous Covid surges.

With 9,382 deaths over the past seven days, the nation's death toll has fallen by 10 percent, week on week.

In the last seven days, the country has recorded 3.4 million cases according to Johns Hopkins data.

The US record during previous waves was 258,000 cases per day, for the week of January 5 to 11, 2021.

Officials have struggled to find a balance that will protect public health without gravely damaging the economy or slamming key services like policing and air travel.

Last week, the US Centers for Disease Control and Prevention halved the isolation period for asymptomatic Covid cases to five days, in a bid to blunt mass Omicron-induced disruption as infections hit new highs in multiple states.

And on Monday, the US Food and Drug Administration approved Pfizer's Covid-19 booster shot for children as young as 12 ahead of the reopening of schools following the holiday break.

Covid-19 has killed at least 5,441,446 people globally since the outbreak emerged in December 2019, according to an AFP tally compiled from official sources on Monday.

Taking into account excess mortality linked to Covid-19, the World Health Organization estimates the overall death toll could be two to three times higher.