Authorities are rushing to investigate three coronavirus cases in NSW as Australians look for interstate travel certainty ahead of Christmas.
NSW was on Wednesday given 48 hours by Queensland authorities to investigate the source of three new mystery cases, which are likely to threaten the state's 12-day run of no community transmission.
NSW needs 28 days of no community transmission before Queensland reopens the borders.
NSW Premier Gladys Berejiklian has again urged her Queensland counterpart to reconsider the "unrealistic" stance.
Queensland Health Minister Steven Miles said there was reason to be concerned the border countdown would be reset.
"But we will monitor very closely whether NSW can link those cases to existing clusters," he told reporters on Wednesday.
Community transmission is preventing Western Australia from opening its borders, with the state remaining closed until 28 days without community spread in eastern states.
Treasurer Josh Frydenberg said the government was confident domestic borders would open by the end of the year, apart from WA, which he expects to open in April.
"Closed borders cost jobs, so the quicker those borders are open in a COVID-safe way, the better, not just for those local communities and those particular states but across the country," he said.
"Queensland has a very dynamic and large tourism sector and that tourism sector is being hurt by those border restrictions."
WA Premier Mark McGowan says the federal government's expectation of an April border reopening is simply an assumption.
Victoria recorded another six new cases on Wednesday, with two of those being investigated to identify the mystery source.
There are ongoing concerns over a case cluster at Chadstone in Melbourne, with a spread from there to the regional town of Kilmore.
Another two people have died from the virus in Victoria, taking the national toll to 897.
There are now 16 Victorians being treated in hospital for COVID-19.
Premier Dan Andrews is urging people to get tested for the virus as a shopping centre outbreak continues to grow.
Melbourne's rolling 14-day new case average has decreased to 9.9, with the city needing it to drop to five, with no more than five mystery cases during the same period, before restrictions can ease further on October 19.
From Thursday, South Australia will extend its buffer zone with Victoria, easing COVID-19 restrictions on border communities.
The zone will increase from 40km to 70km on each side of the border, allowing more people to travel into SA or return from trips into Victoria without the need to quarantine.
© AAP 2020
Photo: SA border 5kms east of Pinnaroo, South Australia. (AAP Image/Kelly Barnes)