The NSW government has hit a major hurdle in its planned sale of WestConnex, with the competition watchdog saying it needs more time to assess it.
The Australian Competition and Consumer Commission was due to make a decision on Transurban's proposed acquisition of the multi-billion dollar toll road on Thursday but will now do so in seven weeks' time.
Chairman Rod Sims said the project was "unusually large" with "unusually complex competition issues".
"We simply require more time to consider," he said in a statement on Thursday.
A final decision will now be made by September 6.
The consortium led by Transurban is one of only two bidders remaining.
The tender was due to close next week, with the government planning on finalising the sale by August.
Mr Sims acknowledged that the delay will cause "quite significant complications" for the NSW government.
"We're sorry about that and aware of that but we've got to get it right," he told reporters.
"We do have competition concerns, they are important concerns."
It's the second time the ACCC has delayed delivering its findings. Its initial decision date was to be in April but the timeline was extended after more information was requested from the company.
"The reality is that this is a major transaction in the context of NSW toll roads, arguably the most significant in Australia in the foreseeable future."
In May, the ACCC identified a number of preliminary concerns with the sale - including the impact Transurban's acquisition could have on future bids for other toll roads.
Transurban - Australia's largest toll road operator - already controls seven of the nine existing toll roads in NSW.
The state government is selling 51 per cent of the $16 billion project, which includes 33 kilometres of motorways and road upgrades.
Labor's roads spokeswoman Jodi McKay called on the government to stop the sale until the ACCC hands down its findings.
"To proceed with the sale would be reckless and irresponsible," she said in a statement.
The NSW treasurer and minister for WestConnex have been contacted for comment.
