South Australia's border restrictions with NSW and the ACT will remain in place with local officials growing increasingly concerned about a COVID-19 "super spreader" outbreak in Sydney.
As SA reported no new infections on Tuesday, Premier Steven Marshall insisted border rules would only be relaxed when it was safe to do so.
Considering the situation in NSW, the state's transition committee had decided not to go ahead with the lifting of the 14-day quarantine measures on July 20, he said.
SA officials are particularly worried about the virus outbreak associated with the Crossroads Hotel at Casula, in southwestern Sydney which now has 28 cases linked to it.
"The super spreader event, which has occurred at the Crossroads Hotel on the Hume Highway is really of great concern," the premier said.
"There are now many hundreds, probably in excess of 1000 people who are now in isolation and we don't have the details on exactly how many people have become infected."
Mr Marshall said he understood the change in the timeline for NSW would inconvenience many people.
"But our primary responsibility is for the health, safety and welfare of all South Australians," he said.
"We're being cautious, we're looking at the epidemiology of what's going on, we're looking at the results in NSW.
"But at this stage, there's too much uncertainty."
SA's decision will also impact on AFL teams planning to travel to Adelaide from Sydney.
SA has already lifted the quarantine restrictions for people coming from Queensland, Tasmania, the Northern Territory and Western Australia.
But it has imposed a hard border closure with Victoria, only allowing locals to return and essential travellers through, because of the surge of infections in Melbourne.
Mr Marshall said SA was still "a long way off" imposing a similar hard border closure with NSW.
But from Saturday, the state government will start charging Australians returning from overseas for the cost of their 14 days of supervised quarantine.
The premier said SA was still keen to participate with the national repatriation program but those arriving from Saturday would be asked to pay for their hotel stay.
Individuals will be charged $3000, with their partners to be billed $1000 and $500 for each child.
Australian Associated Press
