Mr Barr has also called for extra resourcing of the federal agencies responsible for assessing major projects, including the National Capital Authority, as he expressed the ACT government's frustration with the Commonwealth's environmental approvals process.

The chief minister on Friday confirmed the government would not be signing a contract for construction of the next stage of light rail before October's ACT election, with plans for the Alinga Street to Commonwealth Park extension yet to be ticked off by federal environmental authorities.

Mr Barr lamented the complexity of the approval process for light rail's second stage, which he said had been held up to Prime Minister Scott Morrison and Treasurer Josh Frydenberg as a prime example of the obstacles encountered when states and territories were called on to accelerate infrastructure projects.

"It would be fair to observe from the outset that the time frames associated with moving a large infrastructure project through this legislation can indeed be frustrating for proponents," Mr Barr said.

"This is something that we have experienced in recent months and years."

Transport Minister Chris Steel, speaking alongside Mr Barr, said the planning approval process for light rail's extension was among the most complex in Australia's history.

The environmental approvals process is set for an overhaul after national cabinet, of which Mr Barr is a member, last month agreed to new "single-touch" assessment model.

Under the proposal, which has drawn criticism from environmental groups, states would carry out the environmental approvals for major projects, rather than the Commonwealth. Details of how the new model would work are still being thrashed out.

While stressing that projects shouldn't be subject to any less scrutiny, Mr Barr said moves to reduce the number of agencies involved in the assessment process would be a "sensible reform".

"The point that I am making here is not that there doesn't need to be due diligence on this [light rail] project, of course there does," Mr Barr said.

"But as has been highlighted, there are about four different approval agencies required here. What it does show is that in totality this is a very complex approvals process for a major transport infrastructure project in the heart of the CBD of the national capital.

"It does go to highlight how at times in this country ... that these things can take quite a long time."

Mr Barr said boosting staff numbers at the agencies responsible for assessing projects - including the National Capital Authority - would help to avoid potential delays.

"In the simplest possible terms, they need more staff," he said.