Tony Abbott is seeking the support of other world leaders to establish a force to secure the MH17 crash site, warning time was running out to recover victims' remains.
With up to 100 bodies still not recovered from the large impact zone in eastern Ukraine, the Prime Minister again demanded that Russian-backed separatists respect a unanimous United Nations Security Council resolution.
As Foreign Affairs Minister Julie Bishop left New York for the Dutch city of Eindhoven, where she was expected to join Governor-General Sir Peter Cosgrove for the arrival of the bodies of the victims, Mr Abbott said an inspection of bodies transported by train to Kharkiv, Ukraine's second-biggest city, had revealed many victims' bodies remained missing.
"We just don't know how many bodies we have," he said yesterday. "It's quite possible that many bodies are still out there in the open, subject to interference and subject to the ravages of heat and animals. That is the predicament in which we find ourselves."
Mr Abbott, who is believed to have discussed with Cabinet colleagues involving the military in recovering victims' bodies, has asked senior Government officials from "different agencies" to come up with options. He has also canvassed with others leaders ways of securing the site.
"I am conscious of the fact we are talking about a very large site over which wreckage has been strewn, wreckage and bodies," he said. "We are talking about some 50sqkm and yes, it's a dangerous part of the world.
"But I stress, we will work with our partners. We will work under a UN resolution but we will bring them home because that is the duty the Australian Government owes to the Australian people."
The PM said former Defence chief Angus Houston, who is in Kiev co-ordinating the Australian response, had advised the Government that a full search of the crash site was necessary.
Asked whether a new UN resolution would be needed to allow a multinational force to guard the crash site, Mr Abbott referred to paragraph 8 of the resolution: "Insists on the dignified, respectful and professional treatment and recovery of the bodies of the victims, and calls upon all parties to ensure that this happens with immediate effect."
But when it was pointed out that it would take thousands of well armed troops to secure such a large area, Mr Abbott said: "That's entirely speculative and I would discourage you from any speculation along those lines."
Senior Russian military officers have claimed that the Boeing 777 might have been downed by a Ukrainian fighter jet they say was in vicinity of the passenger jet at the time.
But Mr Abbott dismissed the Russian claims as "theories".
"I know there's been all sorts of speculation and new theories - I think that's the most dignified way of describing them," he said.