He has defended the time lag in the notification by New Zealand of the live-fire drills in the Tasman Sea an hour and a half after the Chinese flotilla's window for firing activity opened.
Chief of the Defence Force Admiral David Johnston told a parliamentary hearing on Wednesday the warning from the NZ military, which Australia was relying on to track the warships in the Tasman Sea, came in about 11am on Friday.
Defence only learned of the drills about 40 minutes after the window opened following an alert by a Virgin pilot who heard the emergency broadcast mid-flight, and notified Airservices Australia at 9.58am.
Aviation officials issued a hazard warning two minutes later, and by 10.10am had contacted the defence force.
Asked if there were issues given the time it took to notify the ADF, Mr Marles said he didn't think so.
"Trying to make something of when that information ultimately makes its way to Canberra is not the pertinent point here," he told ABC's Radio National on Thursday.
Asked if it would be alright for New Zealand to take 90 minutes to inform Australia of a threat, Mr Marles said two different circumstances were being conflated.
"No one is suggesting that is what is occurring here," he said.
"So to equate what is going on with the observation of a Chinese exercise with a real threat is not fair."
Mr Marles said the Chinese naval task group was more than 500km west of Hobart, and on the edge of Australia's exclusive economic zone.
He said the government did not know if a submarine was accompanying the Chinese warships.
"That's why submarines matter," he said.
"That's why we're investing heavily in our long-range submarines.
"We can't answer that question definitively, which is precisely why it's important that Australia has a long-range submarine capability."
Under the AUKUS partnership, Australia is set to acquire nuclear-powered submarines in a deal with the US and the UK.
Liberal senator James Paterson grilled officials during Wednesday's hearing, and accused the government of making a false equivalence between the conduct of the Australian military and the People's Liberation Army.
The evidence given at senate estimates also appears to contradict the timeline given by Prime Minister Anthony Albanese.
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