The 2021/22 budget was set to be delivered on August 31, but was delayed due to the COVID-19 outbreak in the ACT, which has seen Canberra in lockdown for two months.

Mr Barr's 10th territory budget, handed down just eight months since his last, is expected to deliver large amounts of infrastructure spending in an attempt to drive the post-lockdown recovery.

A $5 billion infrastructure fund will supercharge 250 projects across the ACT.

Among them is $1.4 billion for transport projects, which include the second stage of Canberra's light rail network.

Meanwhile, more than $800 million has been allocated for health infrastructure, such as planning and designing a new hospital for Canberra's north and a cancer research centre at Canberra Hospital.

Mr Barr said the new investments were an attempt to make the economy go "full throttle".

"We will be pumping hundreds of millions of dollars into the ACT economy over the coming years to support, create and protect thousands of good, secure, local jobs in the public sector, the private sector and the community sector," Mr Barr said.

"Interest rates are the lowest since federation, providing a once-in-a-century opportunity for the government to build sustainable, productivity-improving and growth-enabling infrastructure to prepare our city for the future."

The ACT's deficit was $603 million at the 2020/21 budget released in February, which was $306 million smaller than predicted in August 2020, due to higher GST revenue and a strong housing market.

The deficit for 2021/22 was forecast to reduce to $474.7 million.

But that was before the Delta variant outbreak, which has led to more than 1000 COVID cases in the territory.

The chief minister has previously said he expected to see a boost to the Canberra economy around Christmas.

The ACT's lockdown will lift on October 15, with restrictions to be gradually eased over coming weeks.

Australian Associated Press