WASHINGTON — President Joe Biden's top medical adviser Dr. Anthony Fauci said on Sunday that the United States is "going in the wrong direction" as the number of COVID-19 cases continues to rise, particularly among unvaccinated Americans.

"If you look at the inflection of the curve of new cases and, as you said in the run-in to this interview, that it is among the unvaccinated. And since we have 50 percent of the country is not fully vaccinated, that's a problem," Fauci told CNN's Jake Tapper on "State of the Union" when asked about a model projecting a worst-case scenario of 4,000 deaths a day in the US from COVID-19 if vaccination rates do not improve.

The chief medical adviser to President Joe Biden and the nation's top infectious disease expert added that the majority of those deaths could be among the unvaccinated.

"So it really is, as (US Centers for Disease Control and Prevention) Dr. (Rochelle) Walensky has said many times and I have said, it is really a pandemic among the unvaccinated, so this is an issue predominantly among the unvaccinated, which is the reason why we're out there, practically pleading with the unvaccinated people to go out and get vaccinated," he said.

The warning from Fauci comes as the dangerous Delta variant of Covid-19 sweeps across the nation and health officials caution Americans to remain vigilant in preventing its spread. Every state in the US reported more COVID-19 cases in the week ending Friday than the week prior, according to data from Johns Hopkins University, with the gravity of the situation evident from coast to coast.

Thirty states have yet to fully vaccinate at least half of their residents, according to the CDC. And as of Friday, the daily average of people becoming fully vaccinated was the lowest it had been since the end of January.

CNN previously reported that discussions within the Biden administration on whether to revisit mask guidelines are ongoing and that the CDC is reconsidering its stance on mask orders, according to sources familiar with the talks. Fauci on Sunday said revising mask guidance for vaccinated Americans is under "active consideration" and that he is part of the discussion.

Fauci said local decisions saying vaccinated people should wear a mask, such as those occurring in virus hotspots like Los Angeles County in California, are not incompatible with the CDC's overall recommendation that gives a lot of discretion to local governments.

"We're seeing that in LA. We're seeing that in Chicago. We're seeing that in New Orleans," Fauci said. "The officials there, many of them are saying even if you are vaccinated, it's prudent to wear a mask indoors." — CNN