The NSW premier has slapped down suggestions of a hard border with Victoria amid an outbreak of COVID-19 cases in the state but has advised against travel to Melbourne or its outer-suburban hotspots.
Victoria confirmed another 19 coronavirus cases on Sunday and 16 on Monday, taking to 176 the number of new cases over the past eight days.
Most new Victorian cases came from family gatherings.
NSW Premier Gladys Berejiklian has persistently criticised interstate travel restrictions imposed by states including South Australia and Queensland - however Deputy Premier John Barilaro on Monday said NSW was watching the Victorian situation closely and didn't rule out some travel restrictions.
But Ms Berejiklian later on Monday told reporters she would not agree to border closures with any of NSW's neighbour states.
She nevertheless advised against travel to Melbourne for the time being, particularly its six current coronavirus hotspots - the local government areas of Hume, Casey, Brimbank, Moreland, Cardinia and Darebin.
"We would recommend nobody travel to those hotspots and certainly the Victorian government and Victorian health experts have also suggested to people living in those hotspots not to travel around," Ms Berejiklian said.
"We said from the beginning, once you start easing restrictions, we will expect case numbers to go up.
"I appreciate what Victoria is going through but don't assume that it won't happen in NSW or anywhere else ... it can happen very quickly, just with a couple of cases, a couple of instances of people spreading the virus unintentionally."
Mr Barilaro earlier declined to reject interstate travel restrictions and admitted Victoria's spike in COVID-19 cases was "worrying" and "a real threat".
NSW reported two new cases of coronavirus over the 24 hours to 8pm on Sunday, one in a hotel-quarantined traveller.
The other case was in a man in his 30s from southwest Sydney, with the source of his infection still unknown.
"He's not travelled recently or attended any mass gatherings recently ... he's well and isolating at home," NSW Health's Dr Jeremy McAnulty said in a video statement on Monday.
No COVID-19 patients are currently in intensive care in NSW.
Victorian Health Minister Jenny Mikakos on Sunday announced a four-week state of emergency extension for her state until July 19, with Monday's planned easing of restrictions postponed and gathering limits re-tightened.
Prime Minister Scott Morrison on Monday said it was inevitable there would be some "bumps along the road" in Australia's attempts to suppress COVID-19 and localised outbreaks shouldn't come as a surprise.
"We will continue on with the process of opening up our economy and getting people back into work but there will be setbacks from time to time - we have systems to deal with the set backs," Mr Morrison told reporters.