Millions of Sydneysiders are now preparing for at least another four weeks in lockdown with an announcement set to be made by Premier Gladys Berejiklian on Wednesday.

Health officials reportedly made the decision in crunch crisis talks on Tuesday, after a record 172 new cases were announced.

New South Wales Health flagged a further 49 venues in a late-night public health alert on Tuesday, including 13 supermarkets.

While the west and southwestern suburbs remains the epicentre of the highly contagious Indian Delta outbreak, the focus is now shifting to new areas that had so far been largely unaffected.