WASHINGTON (REUTERS) - California has become the first US state to require that its teachers and other school staff be vaccinated or regularly tested for Covid-19, a move that Governor Gavin Newsom called a responsible step to ensure the safety of children.

The move comes as Texas Governor Greg Abbott's statewide ban on mask mandates hit its second legal setback after a judge in Dallas County temporarily blocked it from being enforced amid a nationwide rise in coronavirus cases.

Mr Abbott and fellow Republican Governor Ron DeSantis of Florida have faced defiance over their statewide orders that prevent local officials from deciding whether to require that masks be worn.

Masks have become a divisive issue, often splitting the country along political lines, despite near universal agreement among health experts that they can limit the spread of the virus.

In Tennessee, more than a hundred anti-mask protesters heckled masked people, including doctors and nurses, on Tuesday (Aug 10) in Williamson County where the school board voted earlier to require masks for elementary students.

A video with nearly 2 million views on Twitter shows the crowd surrounding a masked man as he walked to his car.

The vaccination requirement in California schools follows similar orders that applied to state employees and healthcare workers.

"We think this is a sustainable way to keeping our schools open, and to address the No. 1 anxiety that parents like myself have for young children," Mr Newsom said at a briefing where he was flanked by state teachers' union officials who support the move.

Spurred by the Delta variant, the country's coronavirus cases have spiked to their highest levels in more than six months, according to a Reuters tally. New US cases have increased more than five-fold over the past month with the seven-day average hitting 118,000 on Tuesday.

In response, the US government and several states, along with some hospitals, universities and a growing number of private employers, have said they require employees to get inoculated. The White House said last week that almost 90 per cent of US educators and school staff are vaccinated.

New York City last week become the first major US city to require proof of Covid-19 vaccination at restaurants, gyms and other businesses, starting next month.

In Texas, the temporary order in Dallas issued late on Tuesday by Judge Tonya Parker allows officials in the state's second-most populous county to require masks indoors, despite Mr Abbott's July order against such mandates. A hearing on Aug 24 will determine whether to extend the temporary order.

The top elected official in Dallas County, Judge Clay Jenkins, who sought the court order issued late on Tuesday, said preventative steps such as mask-wearing are needed to combat a spike in new cases of Covid-19.

"Models predict ongoing dramatic increases in cases and hospitalisations over the coming weeks that will exceed the peak earlier this year unless behaviour change takes place," he said on Tuesday on Twitter.

In a written statement, Mr Abbott said that he had asked an appeals court to strike down Mr Jenkins' action on masks, saying it clearly violated his executive order. The Texas Disaster Act, he continued, gives the governor the power to decided on such actions in an emergency.

"The path forward relies on personal responsibility - not government mandates," Mr Abbott said.

Earlier on Tuesday, another Texas court granted an order at least until Monday that enables officials in San Antonio and Bexar Counties to require that masks be worn in public schools.

Oregon and Washington state are also grappling with surges in cases and hospitalisations as the outbreak spreads beyond the epicentre in the US South.

Oregon Governor Kate Brown on Wednesday announced all state executive branch employees must be vaccinated, and she also reimposed a statewide indoor mask mandate.

The latest coronavirus wave is still the worst in Southern states, based on new cases and hospitalisations per capita in recent weeks.

Arkansas, Florida and Louisiana are all reporting record Covid-19 hospitalisations in recent days.

Florida's Broward County school board on Tuesday flouted an order by Mr DeSantis that outlaws mask requirements in the state, prompting the administration of US President Joe Biden, a Democrat, to say it was considering supporting the school districts financially if Mr DeSantis retaliates against them by withholding funds from officials' salaries.