The number of unlinked COVID-19 cases in Sydney will help determine whether the SCG is at 50 per cent capacity for the third cricket Test, which Prime Minister Scott Morrison says he would love to attend.

NSW reported three new cases of COVID-19 community transmission on Friday.

However, all three cases are from western Sydney and yet to be linked to the cluster on the Northern Beaches.

The state is also concerned sewage testing in Wollongong has picked up fragments of the virus.

The four-Test series between Australia and India resumes at the SCG on Thursday, with Cricket Australia’s board opting against a late change to its schedule.

The NSW government remains confident fans will be able to attend the match.

NSW Opposition Leader Jodi McKay, health expert Norman Swan and some epidemiologists have questioned whether that is wise.

But the state’s stance drew support from the highest office in the country on New Year’s Day.

“I have great confidence in the decisions the NSW government is making in relation to these matters,” Scott Morrison told reporters.

“Whatever level of crowd they ultimately decide is appropriate for that public event, I am sure will be based on health advice.

“On that basis, I’m comfortable with those decisions.

“If I was in Sydney, I would love to go there and sing the national anthem in its new form.”

Border restrictions will likely ensure Mr Morrison does not attend the third Test.

Mr Morrison said he had exchanged text messages with Australia’s captain Tim Paine and coach Justin Langer on Friday, when the health crisis ensured there was no Kirribilli meet and greet with the Test squad.

Current restrictions will allow cricket fans to attend the SCG, provided they are not from certain postcodes and agree to wear a mask when not seated.

However, NSW Premier Gladys Berejiklian reiterated on Friday that “this pandemic is an evolving situation and every day things can change”.

“The government will consider new settings if we need to. Every day the government will make decisions and move swiftly if we feel we need to,” Ms Berejiklian said.

“That includes looking at events, looking at venues.

“If we get to a stage where there’s too many cases that are completely unlinked then of course we’ll adjust.”

The Premier added “we are always concerned when cases pop up, which we can’t establish a link for”.

“That’s why those cases in western Sydney are a big concern for us,” Ms Berejiklian said.

“But in NSW, we make sure that we adjust our settings based on the health advice.

“Based on the rates of testing, whether we can establish links … there’s a number of things we look at.”

-AAP