A highly contagious sub-variant of the Omicron variant of COVID-19, known as BA.2, could soon lead to another uptick in coronavirus cases in the US, the country's top infectious disease expert has warned.

White House Chief Medical Advisor Dr. Anthony Fauci said the subvariant is estimated to account for around 30 per cent of all new cases in the US, and is also the most dominant variant in the country, CNBC reported on Sunday.

Fauci said BA.2 is about 60 per cent more transmissible than Omicron, but it does not appear to be more severe.

"It does have an increased transmission capability," Fauci said on Sunday on ABC's This Week. "However, when you look at the cases, they do not appear to be any more severe and they do not appear to evade immune responses either from vaccines or prior infections," he explained.

Fauci said that vaccines and booster shots remain the best means to prevent serious illness from the virus.

The variant has already caused a surge in cases in China and parts of Europe.

Indian-origin US Surgeon General Vivek Murthy on Sunday expressed concern over the lack of funding to fight the coronavirus pandemic.

"When we look at what's happening around the world and over the last two years, we recognise that when cases increase in one part of the world, that often leads to increases in the other part of the world. And we should be prepared that, you know, COVID-19 hasn't gone away," he told Fox News in an interview.

"There may be rises and falls in cases in the months ahead. But here's the key, our goal is to keep people out of the hospital, it's to save their lives, and we have more tools to do that than ever before. So, our focus should be on preparation, not on panic. And if we get people these tools, vaccines, boosters, treatments, then we can actually get through waves that may come and go.

"The thing that concerns me right now is that as much work as we've done in the last two years to get the right tools, we've got to continue funding them and supporting them so they are available to people across the country. That's what Congress moving to provide that funding is so cortical," Murthy explained.

The US Centres for Disease Control and Prevention reported more than 31,200 new COVID-19 cases on Saturday, including 958 deaths.