White House virus adviser Dr Birx warns both rural and urban areas are experiencing a surge in cases. The Covid-19 task force head has been accused of being complicit in virus disinformation spread by President Trump by top Democrat Nancy Pelosi.
The United States has entered a "new phase" of the pandemic, with rural areas just as threatened as major cities.
Dr Deborah Birx, who heads the White House coronavirus task force, told CNN's "State of the Union" on Sunday that local virus mitigation procedures were starting to work, but added that "what we are seeing today is different from March and April".
"It is extraordinarily widespread. It's into the rural as equal urban areas," she added. "To everybody who lives in a rural area, you are not immune or protected from this virus."
"We are in a new phase," Birx said.
She added that sticking to health and safety guidelines, such as wearing a mask, maintaining personal hygiene and observing social distancing, was crucial.
As of Sunday, the US had tallied more than 4,813,647 cases of Covid-19 and 158,365 deaths, according to various virus trackers, making it by far the hardest-hit country in the world.
The US notched 47,508 new cases on Sunday, a slight dip from the previous five days, which had all recorded more than 60,000 new infections.
READ MORE: Latest global Covid-19 updates
'No confidence in Birx'
US House Speaker Nancy Pelosi said earlier on Sunday that she does not have confidence in Birx, linking her to disinformation about the virus spread by President Donald Trump.
"I think the president has been spreading disinformation about the virus and she is his appointee so, I don't have confidence there, no," Speaker Pelosi told ABC's "This Week" when asked if she has confidence in Birx.
Birx, asked about Pelosi's comment during the CNN interview, said she had great respect for Pelosi and attributed the criticism to a New York Times article on the White House pandemic response that described Birx as having embraced overly optimistic assessments on the virus.
"This was not a pollyannish view. I’ve never been called pollyannish, or non-scientific, or non-data driven," Birx said.
"I will stake my 40-year career on those fundamental principles of using data to implement better programmes and save lives."
According to a report in Politico, Pelosi attacked Birx's credibility during a meeting last week with Treasury Secretary Steve Mnuchin and White House Chief of Staff Mark Meadows.
She accused Birx of spreading disinformation about the coronavirus pandemic while praising Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases as "a hero," Politico said.
"Deborah Birx is the worst. Wow, what horrible hands you’re in," Pelosi told them, according to Politico.
The US Republicans and Democrats are facing off over a deal for the next round of legislation to provide relief to Americans hit hard by the pandemic.
Both sides said on Saturday they had their most positive talks yet. But there was no sign of movement on the biggest sticking point – $600 per week in extra federal unemployment benefits for Americans that has been a lifeline for millions of jobless Americans and expired on Friday.
Experts say the US can afford to pay large sums for coronavirus relief efforts and should lock down the nation for four to six weeks to help stem the virus spread.