The U.S. reported 251,781 COVID-19 cases among kids during the week ending Sept. 2 -- the highest week of pediatric cases since the pandemic began, according to the weekly report from the American Academy of Pediatrics and the Children’s Hospital Association.

After declining in the early summer, new cases among kids are rising "exponentially," the organizations wrote, with the weekly figure now standing nearly 300 times higher than it was in June, when just 8,400 pediatric cases were reported over the span of one week.

Last week children represented 26.8% of all reported COVID-19 cases. Regionally, the South had the highest number pediatric cases, accounting for approximately 140,000 of last week's cases.

The rate of pediatric hospital admissions per 100,000 people is also at one of its highest points of the pandemic, up by 600% since the 4th of July, according to federal data.

Severe illness due to COVID-19 remains "uncommon" among children, the two organizations wrote in the report. According to the nearly two dozen states which reported pediatric hospitalizations, 0.1%-1.9% of all child COVID-19 cases resulted in hospitalization. ​Similarly, in states which reported virus-related deaths by age, 0.00%-0.03% of all child COVID-19 cases resulted in death.

However, the AAP and CHA warned that there is an urgent need to collect more data on the long-term consequences of the pandemic on children, "including ways the virus may harm the long-term physical health of infected children, as well as its emotional and mental health effects."

About 37.7% of children ages 12 to 15 and 46.4% of adolescents ages 16 to 17 have been fully vaccinated against COVID-19.

-ABC News' Arielle Mitropoulos

The country's daily death average continues to surge, now standing at more than 1,100 deaths reported a day. This marks the nation's highest average in nearly six months.

On Tuesday, the death toll crossed 650,000 Americans lost to the virus, according to data from Johns Hopkins University, meaning that 1 in every 504 Americans has died from the virus.

The U.S. COVID death toll is now more than 218 times higher than the number of lives lost during the U.S. attacks on Sept. 11. It is also rapidly approaching the total number of American deaths that were recorded during the 1918 influenza pandemic.

Prior to the Labor Day holiday, the U.S. daily case average stood around 150,000 cases a day. About a year ago, around Labor Day, the country was averaging about 38,000 new cases a day.

-ABC News' Arielle Mitropoulos

Tucson, Arizona, officials announced a pause on the city's policy to require its public employees to receive a COVID-19 vaccine after Arizona Attorney General Mark Brnovich called it illegal and threatened to cut funding if the city went through with the plan.

Tuscon City Manager Michael Ortega said in a statement the city council is evaluating the mandate's legal position.

"Until we have a better understanding of our legal position in relation to today’s report, I have instructed staff to pause on the implementation of the policy," he said.

Brnovich said Tuscon's rule violated Gov. Doug Ducey's July executive order that banned any state or local office from requiring their staff get a vaccine against the coronavirus or any vaccine that has only received an emergency order.

"COVID-19 vaccinations should be a choice, not a government mandate," he said in a statement.

Tucson Mayor Regina Romero said in a statement that the attorney general was "prioritizing his political ambitions over his responsibility to objectively interpret the law."

As of Tuesday, over 606,000 residents in Pima County, Arizona, the county that includes Tucson, have had one COVID-19 shot, according to the Pima County Health Department. That represents roughly 56.7% of the county's 1.07 million population, according to the U.S. Census numbers.

The county has recorded more than 4,000 new cases since Aug. 5, according to health department data.

-ABC News' Ali Dukakis

Idaho hospital officials are pleading for the public to get vaccinated and take COVID-19 warnings seriously after the state declared a crisis in its standards of care.

Kootenai Health, a northern Idaho hospital, currently has 113 patients with COVID-19, an increase from the 90 patients they had last week, officials said. Administrators had to set up 22 beds in a conference room to deal with the influx of patients.

Dr. Robert Scoggins the chief of staff at Kootenai Health, said the hospital was not built for a pandemic this size. Currently, 39 patients are in the intensive care units and 19 are on ventilators, all on high levels of oxygen, he said.

The hospital said it could see as many as 140 patients in the coming weeks.

"The message that I’d like to send out to people is that we’re near the limit that we can handle in this facility," Scoggins said in a news conference. "We’ve done a lot of things to expand our care to take care of more patients, but it keeps growing. If we had everyone in the community vaccinated, we would not be in this position.”

-ABC News' Flor Tolentino and Nicholas Kerr