The state's COVID crisis is worsening and 100 people have died in the latest outbreak which began mid-June.

There are 917 COVID-19 patients in hospital, with 150 in intensive care, 66 of whom require ventilation and hospitalisations are predicted to peak in October.

Premier Gladys Berejiklian says the state needs to brace for the situation to deteriorate.

"The most recent advice I've received is that case numbers are likely to continue to rise for the next few weeks and the worst hospitalisation rate is likely to be in October," she said on Wednesday.

ICU nurse Michelle Rosentreter says 18 months into the pandemic the system "wasn't really ready for the amount of presentations that we're getting now".

While staff from other wards were trained in ICU during last year's outbreak, they had since returned to other areas of the health system.

Coronavirus patients put extra stress on the system because they often stay in ICU for weeks in addition to the regular ICU patients.

"You're stacked quite heavily with those intensive care patients," she told ABC radio.

"So you now have a high reliance on overtime and double shifts ... and we have got some deployed staff coming back to us now," she said.

"But we're in the thick of it. We're racing not pacing and we know that this isn't going away."

Ms Berejiklian and Health Minister Brad Hazzard say that while the system is under stress, it will cope with the expected surge in COVID-19 patients.

Ms Rosentreter says the plans are "not as solid or robust as the health minister or the premier would believe it is".

"And that's because we've always relied on a minimum staffing ....we don't have big cohorts of nurses and doctors and support people," she said.

"Look, I think we'll hold the line for a while .... but they're going to be a lot more tired and fatigued because we already are.

"We will deliver the best ... care that we can but we won't be able to do it for the long haul."

While staff can be redeployed, that will lead to deficits in other areas.

"You're only moving around resources within a boundary that you've got," she said.

Australian Associated Press