NSW Premier Gladys Berejiklian is expected to announce on Wednesday that Sydney, the Blue Mountains and areas of region NSW will remain in lockdown for another week.

An ACT Health spokeswoman said there would be an update on the current mask requirements before Friday.

"ACT Health is assessing the situation across Sydney and regional NSW regarding when the requirement to wear masks in certain settings will be lifted in the territory," the spokeswoman said.

"ACT Health is assessing a number of factors which will inform whether the ACT will remove the current face masks requirement."

Changing the requirements would also depend on the number of new cases and contacts, the level of community transmission and movement between exposure sites and the ACT and the risk posed to the community.

Masks became mandatory for many indoor settings in the ACT from June 28 in response to the outbreak in Sydney.

Premier Gladys Berejiklian said on Tuesday she would be consulting with health experts throughout the day and into Tuesday evening, with hopes of telling the community on Wednesday "what next week looks like".

NSW recorded 18 new COVID-19 cases in the 24 hours to 8pm on Monday, with seven in the community for at least some of their infectious period, bringing the total number of people infected in the latest outbreak to 330.

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It's a significant drop from the 35 cases the previous day and the premier says "the lockdown is having its desired effect ... but it's still concerning that a number of cases are remaining infectious in the community for that period of time".

The stay-at-home orders for more than five million people in Greater Sydney, Wollongong, Shellharbour, the Central Coast and the Blue Mountains regions are due to end at midnight on Friday.

Ms Berejiklian said on Tuesday that the length of the lockdown would be informed by the fact that the NSW government wants it to be the state's last.

"We intend for this lockdown to be the only lockdown we go through," she said.

She warned that due to the virulence of the Delta strain, restrictions may persist until a good majority of the population is vaccinated.

"When we do come out of the lockdown it won't be what life looked like necessarily before we went into lockdown," she said.

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