Greater Sydney and surrounding regions are in lockdown until at least August 28, as health authorities battle to contain a outbreak of the virulent Delta strain.

"By far the majority were in southwest Sydney and western Sydney," said NSW Health Minister Brad Hazzard.

Mr Hazzard warned that the "Delta variant is partial to younger people".

Some 138 of the cases recorded in the 24 hours to 8pm on Friday are people under the age of 40.

Meanwhile, Sydney construction projects are waking from an enforced, fortnight-long slumber but building industry figures warn it will barely be able to function.

Work was allowed to resume from Saturday morning on non-occupied sites, provided COVID-safe plans are in force.

But the sector cannot call on 68,000 workers from eight council areas worst-hit by the city's coronavirus outbreak.

Most COVID-19 cases are in the eight areas subjected to the locked-down city's tightest restrictions, including mandatory mask-wearing outside the home and distance limits on movements for shopping and exercise.

Construction workers living within, who make up about 42 per cent of the industry's citywide workforce, also cannot work.

"This is a highly limited return to work for the construction industry but something is certainly better than nothing at all," Urban Taskforce chief executive Tom Forrest said.

The state's workplace safety regulator says construction sites should expect a visit to ensure they're complying with public health orders.

"SafeWork NSW will work with businesses to help them understand the rules - and will penalise firms blatantly making no effort to comply," the organisation's Director of Construction Metropolitan, Meagan McCool, said.

Meanwhile, the city's public hospitals have begun postponing non-urgent elective surgeries to cope with the outbreak.

Some 58 COVID-19 patients are being treated in intensive care beds, with 40 per cent needing ventilation.

While the state has 500 ICU beds, NSW Health says stopping some elective surgeries from Monday will increase capacity for other health services.

The change will not affect theatres in Illawarra or Central Coast hospitals.

In Sydney's east, nine businesses at Bondi Beach have been banned from selling takeaway liquor for a week over concerns they were encouraging people to breach public health orders.

Dimitri Argeres, a compliance director at Liquor & Gaming NSW, said the activity of selling cocktails in disposable cups to people to drink as they walked to the next local beachside bar did not pass the pub test.

"It's not appropriate for this type of risky activity to continue given all our efforts and the sacrifices being made across Greater Sydney to reduce the community transmission of the COVID-19 Delta variant," he said.

A new, walk-in AstraZeneca vaccination clinic at Bankstown Sports Club opens for its first full day on Saturday.

Operating 8am to 5pm, it's one of 13 walk-in clinics across the west and southwest. Up to four will be open each day.

Australian Associated Press