NSW has recorded 77 new community Covid-19 cases.

Of these locally acquired cases, 55 are linked to a known case or cluster – 39 are household contacts and 16 are close contacts – and the source of infection for 22 cases remains under investigation.

There have been 566 community cases reported since 16 June 2021, when the first case in the Bondi cluster was reported.

The state yesterday recorded 50 new locally acquired cases - the highest daily tally since the latest Sydney outbreak began.

Of those 50 cases, 26 were infectious in the community prior to their diagnosis.

NSW-NZ flights on hold

Covid-19 Response Minister Chris Hipkins announced on Friday that flights from NSW would be postponed for at least three days.

The flights were due to begin bringing New Zealanders home from midnight on Friday.

When the flights resume, returnees will have to spend 14 days in a managed isolation hotel, although they will not have to pay for their stay.

Premier urged to call in military

Earlier today, NSW Premier Gladys Berejiklian was urged to call in the military to enforce a total lockdown in greater Sydney as a last-ditch effort to control the outbreak.

Epidemiologist Tony Blakely told news.com.au that the state faces three grim choices: the 'let it rip' approach, allowing the Delta variant to circulate in the community; continuing with a partial lockdown with many retail stores still open; or sending in the troops and more police.

Divisions have emerged in recent days in the NSW Government amid reports there was opposition to extending the lockdown, including from Treasurer Dominic Perrottet, who is working on a major rescue and support package for businesses and workers.

But Berejiklian has warned that allowing the virus to circulate is simply not an option until a majority of the adult population is vaccinated.

"They can shrug their shoulders and say, 'we can't control it'. That would be horrific. Thousands of deaths, health services overwhelmed," Dr Blakely said.

"Other countries now that are doing that have already got a lot of immunity either through vaccination or infection. In the UK, remember when they first relaxed last year?

"If NSW did that now it would be far worse per capita because this virus is so much more infectious. The Federal Government and the states would have to redirect vaccines and just put it into NSW. That's just not pretty."

The Melbourne University epidemiologist insisted the only "real option" now is to plunge the state into an even tougher, draconian lockdown for the next fortnight.

Many of Sydney's transmission sites in recent days have been retail centres, including Ikea, which has remained open. "Non-essential" stores such as lingerie shops have also remained open.

"The third option is the only one," Blakely said. "It's very hard to say those words: 'We're going into a hard lockdown, we've called in the military, the police and we are going to police it.'

"It's not a pretty look but if you want it to be over and done with as quickly as possible that, most unfortunately, is what needs to happen.

"If they keep going the way they are now, without really stepping it up now, it could go on for months," he said.

Any decision to call in the Australian Defence Force would require the NSW Premier to request assistance from the Morrison Government.

Despite a fortnight of lockdown, daily case numbers are now running at 10 times the daily infection rate first reported in late June, when Sydney was recording only five cases a day.

As a result, there are now more than 14,000 close contacts in isolation and millions of citizens in Sydney and other local government areas locked down in their homes.

Residents are also now prohibited from travelling more than 10km from their family home and are facing ID checks in the streets to prove where they live.