The ACT's coronavirus outbreak has grown to 28, with new cases including at an aged care home and another school.

The territory's seven-day lockdown has been extended for another two weeks until September 2.

Federal parliament is due to return next week, but the Territory Chief Minister Andrew Barr wants Prime Minister Scott Morrison to reconsider.

"They need to consider the urgency of a federal parliamentary sitting and whether it is required," he told reporters on Monday.

"My preference would be that they don't unless they absolutely have to. And if they did, it would need to be a very minimal sitting and absolutely COVID safe.

"But my starting point would be now is probably not the time for the federal parliament to return."

The ACT health rules didn't prevent parliament from sitting because was considered an essential workplace.

Mr Barr discussed the possibility of delaying parliament with both federal leaders.

Labor leader Anthony Albanese indicated he supported putting off the next sitting fortnight.

"Common sense will prevail here. It would be very difficult to get people here in order for parliament to sit," Mr Albanese said.

COVID-19 has reached the ACT's aged care system for the first time.

A worker from the Tuggeranong Greenway Views Village did three shifts last week without realising they had the virus.

The centre was locked down and authorities hoped the fact the worker was partially vaccinated would limit the spread.

Meanwhile, a Lyneham High School student last week attended classes for four days while infectious.

This prompted quarantine orders for staff, students and their households.

Gold Creek School, Holy Spirit Catholic Primary School and the rehearsal room of the University of Canberra High School Kaleen were also among more than 80 exposure sites.

Across the territory, about 6500 close contacts had been identified with 5723 tests conducted on Sunday.

About 1800 people were in quarantine after returning from NSW, which reported 478 new cases and eight additional deaths including a teenage boy.

Mr Barr warned ACT residents to expect more cases in coming days and indicated the territory's budget would likely be delayed.

Canberra's lockdown had been slated to expire this Thursday following its first case in 13 months.

"This is a serious situation," Mr Barr said.

"We do not want to see the numbers continue to grow. We do not want to see exponential growth as we have seen in other jurisdictions."

It remains unclear exactly how Canberra's initial case, a man in his 20s from Gungahlin, contracted the Delta variant.

But the infection was linked to Sydney's outbreak.

Australian Associated Press