NSW Premier Gladys Berejiklian doesn't believe her state's restrictions on border communities are too tough.

In her Monday press conference in Sydney, Ms Berejiklian acknowledged those who "go down to" border communities would find people "angry with me".

But she said tough border measures were necessary because of the state's proximity to the coronavirus situation in Victoria

She also didn't rule out further steps.

"If you ask the border communities, they'll tell you I'm being too tough, in not being relaxed enough for these border communities," she said.

"I don't think we're being too tough, I think our response is adequate, but if we have to do more, we will."

Ms Berejiklian referred to the Crossroads Hotel outbreak, where one positive case ultimately led to a contact tracing effort that reached 600 people.

She told NSW residents to be on "extra high alert" and the next few weeks were said to be critical.

NSW added 13 new cases of COVID-19 in Monday's update, three of which were in hotel quarantine and one was a person who had travelled from Victoria.

Of the others, one could not be traced to an existing cluster.

The state's advice from Sunday was to strongly encourage residents to use masks where social distancing isn't possible.