NEW YORK - The United States needs to be prepared to do "anything and everything" to fight the Omicron COVID-19 variant, but it's still "too early to say" whether lockdowns or new mandates will be appropriate, said US infectious disease expert Anthony Fauci on ABC's "This Week" aired on Sunday.

"Inevitably, it will be here. The question is will we be prepared for it? If and when, and it's going to be when, it comes here hopefully we will be ready for it," said Fauci, who is reportedly to meet on Sunday with US President Joe Biden and his COVID-19 response team to discuss the variant and the administration's response.

Meanwhile, Fauci, chief medical adviser to Biden, warned that the United States could potentially experience a fifth wave of coronavirus infections, but said increasing the number of Americans who are vaccinated against the virus and receive their booster shots could blunt its severity.

"We certainly have the potential to go into a fifth wave," Fauci said on CBS's "Face the Nation" aired on Sunday. "And the fifth wave, or the magnitude of any increase, if you want to call it that it will turn into a wave, will really be dependent upon what we do in the next few weeks to a couple of months."

Fauci, also director of the National Institute of Allergy and Infectious Diseases, said there are 62 million Americans who are eligible to be vaccinated against COVID-19 but have not yet gotten their shots, and millions more immunized at least six months ago are now seeing their immunity wane, precipitating the need for booster shots.

Soon after Omicron's discovery, the United States said it would restrict travel for non-US citizens from South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique and Malawi, while major COVID-19 vaccine makers promised to prepare tailored doses to help encounter a potential coronavirus wave caused by the variant.

The World Health Organization last week classified Omicron as a "variant of concern," meaning it is more contagious, more virulent or more skilled at evading public health measures, vaccines and therapeutics. The variant, first discovered in South Africa, has several mutations to the spike protein that allows the virus to enter the body.