"They're recommendations to make sure we keep NSW in the position we are in. I cannot stress enough how critical the next few weeks are."
Elderly people or those suffering underlying health issues should also wear masks.
Prime Minister Scott Morrison on Sunday posted a photo to social media of himself wearing a face mask.
“(The mask) protects others you come in contact with in enclosed areas, in particular the retail salespeople just doing their jobs.
“Not a lot to ask. All in this together,” he said.
But Ms Berejiklian stopped short of making masks compulsory.
"We have been talking about masks for several weeks but obviously the persistent situation in Victoria gives us cause for alarm," she said.
Meanwhile, a Newcastle pub was closed on Sunday for deep cleaning after a COVID-19 positive person from Sydney visited on Thursday.
Wallsend Diggers CEO John Hume said he was contacted by NSW Health on Sunday and advised the person had been in the club last Thursday between 7pm and 9pm.
Mr Hume said every visitor on that evening had been identified and NSW Health was contacting them.
"We have also been advised that we are not the only venue in the area that has been shut down as a result of this person at this stage," he posted on Facebook.
The club is expected to re-open on Monday.
NSW recorded 12 new virus cases in the 24 hours to 8pm on Saturday from almost 22,500 tests.
One case had no known source, with NSW Health's Dr Jeremy McAnulty revealing seven cases in the prior week were not linked to known cases.
Eight people with the virus are in intensive care.
An 83-year-old man connected to the Crossroads Hotel cluster in southwestern Sydney died at the weekend, taking the NSW death toll to 52 and the nationwide tally past 200.
It was the first coronavirus-related death in NSW since late May.
NSW Health on Sunday confirmed a person with coronavirus attended the Advance Early Learning centre in Merrylands, in western Sydney, between July 27 and 29, prompting the childcare centre to close for cleaning.
The Thai Rock Wetherill Park cluster is nearing 100 cases, while the cluster in east suburban Potts Point has reached 24.
People in Australia must stay at least 1.5 metres away from others. Check your state’s restrictions on gathering limits.
If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080. News and information is available in 63 languages at sbs.com.au/coronavirus