Mike Pence, the US Vice-President, played down concern over the rise in infections and called fears of a second wave of the virus "overblown".
In an article for the Wall Street Journal, Pence, who leads the White House coronavirus task force, blamed the media for trying "to scare the American people" and claimed that the US Government was "winning the fight against the invisible enemy".
Pence argued that the states with more than 1000 new daily cases have seen an increase in testing, with officials containing most of the outbreaks.
However, Dr Anthony Fauci, America's top infectious disease expert and a leading member of the coronavirus task force, appeared to dispute Pence's assessment of the situation in a separate interview with the WSJ.
Fauci said that while more testing does lead to more reported cases, the higher percentages of people testing positive in many states "cannot be explained by increased testing".
He added: "People keep talking about a second wave. We're still in a first wave."
Fauci also weighed into the debate over President Donald Trump's first campaign rally since the pandemic began, which is scheduled to take place in Tulsa, Oklahoma, on Sunday NZT.
State officials have asked the President to cancel the indoor event, which 20,000 people are expected to attend, warning it could become a "super spreader" at a time when the state is already seeing a worrying spike in infections.
Asked if he would attend Trump's rally, Fauci told the Daily Beast: "I'm in a high-risk category. Personally, I would not. Of course not."
The 79-year-old added that in terms of safety considerations, "outside is better than inside, no crowd is better than a big crowd".
Pence said the campaign was considering holding the rally at an outdoor venue.
Researchers behind a modelling study used by the White House coronavirus task force have warned that the outbreaks are moving along the country's major highway routes as people travel more.
According to PolicyLab, a research team at the Children's Hospital of Philadelphia, the disease has appeared to spread from south to north along major traffic corridors such as the I-95 interstate road on the east coast and the I-85 interstate road in the southern US.
The findings have raised fears that the outbreaks in the southern US could soon move to major regions on the north-east coast, which have made progress in reducing infection rates.
Governors in some of the worst-affected states have defended themselves, arguing the spikes are down to an increase in testing.
In Florida, some of the increase has been linked to reopened bars, where people anxious to get out after months of seclusion crowded together indoors.
However, Ron DeSantis, the state's Governor, attributed the rise to more widespread testing and dismissed suggestions that it stemmed from Florida's early reopening of bars and restaurants. "We're not shutting down," he told reporters, "You have to have society function."
Greg Abbott, the Governor of Texas, one of the first states to ease restrictions, said the new daily high could be explained by a backlog of cases.
Abbott also blamed young people for the increase, saying many people under the age of 30 have taken a relaxed approach to wearing masks and social distancing while out at bars.
However, Abbott refrained from making the use of face masks mandatory, despite the mayors of nine Texas cities urging him to do so.
In Oregon, more than 200 cases were linked to the Lighthouse United Pentecostal Church in eastern Oregon.
According to the Oregonian newspaper, a now deleted video on the church's Facebook page from May 24 showed hundreds of people standing close together singing. Large gatherings were not permitted at the time.
