A lockdown in regional NSW has been extended until September 10 as Deputy Premier John Barilaro warns "we are on a knife-edge in the regions".

A lockdown in regional NSW has been extended by two weeks as Deputy Premier John Barilaro warns rural communities are "a tinderbox ready to explode" with COVID-19 cases.

Premier Gladys Berejiklian says the decision was made because western NSW remained the area of most concern in the regions, while cases had stabilised in other rural areas.

"Given that acute situation in Dubbo, in particular, the region lockdown will be extended to all of regional NSW until at least midnight, Friday the 10th of September," she said on Thursday.

Most of regional NSW has been in lockdown for a fortnight.

It was due to end on Saturday, but there are now 309 cases in Dubbo in the state's west where vaccination rates are low - around six per cent in the vulnerable Indigenous community.

Twenty-four new cases were recorded in Dubbo overnight.

Local MP Dugald Sanders acknowledged a return to zero COVID cases was "unreachable" but said an extension of the lockdown would be an opportunity to get numbers lower.

Around 60 per cent of cases in the Western Local Health District are in Aboriginal people.

Wilcannia saw five new cases overnight.

Mr Barilaro said it was necessary to extend the lockdown to protect regional communities.

"We're sitting on a knife-edge. It's a tinderbox ready to explode," he said.

He apologised to communities that didn't have any new COVID-19 cases, which will be caught up in the lockdown, but said the decision would also ensure "we don't overwhelm the system".

"One of the reasons you may not have cases is because of the restrictions in place, minimising movement, because we know we're a very interconnected community in regional and rural NSW," Mr Barilaro said.

"Now is the time to stay united and work to those restrictions."

Health Minister Brad Hazzard said "everything that is done should be done and is being done" to support rural health services.

Some 18 people are hospitalised in western NSW, including one who is ventilated.

Health worker numbers have been impacted as 134 staff are forced to isolate, 21 of whom were exposed to the virus at work.

NSW Chief Health Officer Kerry Chant endorsed the extension of the regional lockdown.

"At the moment, with our stretched system, we do not want to be fighting bushfires on multiple fronts," she said.

Of the record 1029 locally acquired cases reported across the state on Wednesday, 35 were in the Western NSW Local Health District, bringing the total number of cases there to 389.

There were 71 cases in the Nepean Blue Mountains district, six in the Far West, two in Illawarra Shoalhaven, and two on the Central Coast.

There were no new cases in the Hunter New England district.

NSW Health's ongoing sewage surveillance program has recently detected fragments of the virus at the sewage treatment plants in Tamworth, Merimbula, Cooma and Brewarrina.

Authorities are concerned because there are no known cases in these areas.