John Barilaro said he thought the border checkpoint was functioning well but did question its necessity.

"Is it necessary? I don't believe borders should be switched on and off like a light switch. But in saying that, we know the spread of the coronavirus has significant impacts and all borders are invisible to the pandemic," he said.

"It's a decision by the ACT government but I do believe they are rolling it out in a very practical way."

Mr Barilaro said if the Sydney outbreak worsened and the ACT decided to strengthen border controls that a permit system could be necessary.

"We're confident we'll get on top of it but if this was the opposite and things were going to get worse I think you would have to look at more permanent arrangements and a permit system could be it," he said on ABC Canberra.

"I'm confident the ACT government is watching what's happening in NSW on a daily basis and are being very flexible and they'll either ramp up or ramp back."

It came after Goulburn Mulwaree mayor Bob Kirk said he would consider asking the ACT government to implement a border system if issues persisted.

Queues of cars have faced delays at the entrance to the ACT from the Federal Highway since Saturday. Some have reported lines which have taken more than three hours to get through.

NSW recorded four locally acquired cases in the 24 hours to 8pm on Monday. Two were connected to the Berala cluster, one was under investigation but was likely connected to the Berala cluster and the other was a household contact of a Croydon case.