A top public health official in the United States has warned that the country is "failing" on Covid-19, after the country recorded its highest daily case load in six months.

"We should not really have ever got to the place we are," Francis Collins, director of the National Institutes of Health, said on ABC's "This Week."

"In that regard, yes, we are failing."

A surge in the highly transmissible Delta variant has brought a slew of bad news: total daily new cases have soared to 118,000, their highest since February; deaths are up 89% over the past two weeks, even while slightly declining around the world; and children's hospitals in US states like Florida are being overwhelmed as young people are increasingly affected.

Fears about the Delta variant have sparked a surge in vaccination rates. Yet millions, especially in conservative areas, remain sceptical about the vaccines.

"We would not be in the place we are right now with this Delta surge if we had been more effective in getting everybody" vaccinated, Mr Collins said.

"Now we're paying a terrible price."

Another top health official, Anthony Fauci, meantime pointed to possible final approval of key vaccines from the federal Food and Drug Administration as early as this month - something some sceptics have said they need to hear.

"I hope that it's within the month of August," Dr Fauci told NBC's "Meet the Press."

The infectious disease specialist, who advises President Joe Biden on health matters, warned that failure to bring the Delta variant under control would increase the chances of a new variant emerging which "could be more problematic than Delta."

Children under 12 are not yet eligible for the vaccines, and Mr Collins said the number of children hospitalised with Covid has hit an all-time high of 1,450.

He warned that if the millions of children soon returning to in-person schooling are not required to wear masks, "this virus will spread more widely.

"It will probably result in outbreaks in schools, and kids will have to go back to remote learning, which is the one thing we want to prevent."

The US Centers for Disease Control said on Twitter that even asymptomatic children can spread Covid-19, adding, "Children 2 years or older should wear masks in public indoor settings, including schools."

US Education Secretary Miguel Cardona seconded that advice. "Let our education leaders lead," he said on CBS's "Face the Nation."

Yet in Florida, one of the states hardest-hit by the latest surge, Governor Ron DeSantis sparked a political furore when he issued an order barring the state's school districts from mandating mask-wearing.

However with hospitals in the state struggling under a fast-growing patient load, a handful of school districts said they would defy the order.

"Our children's hospitals are completely overwhelmed," Aileen Marty, an infectious disease expert at Florida International University, told CNN. "Our pediatricians, the nurses, the staff, are exhausted, and the children are suffering. And it is absolutely devastating."

Mr Collins, for his part, expressed exasperation that the debates over vaccine and mask-wearing had become politicised.

"We don't really need to be polarized about a virus that's killing people. We ought to be doing everything we can to save lives. And that means get the vaccine. And that means wear the mask when you're indoors in a crowded space."

He added: "This is not a political statement or an invasion of your liberties. This is a life-saving medical device."