Defence expects west Mosul will be reclaimed from Islamic State militants by the middle of the year.
While east Mosul has been liberated, an estimated 750,000 civilians are under siege across the Tigris River in the city's west.
So far Iraqi forces are in control of 30 per cent of the city's west.
"By mid-year would be the expectation that west Mosul is cleared," Australia's chief military operations planner David Johnston told the Australian Strategic Policy Institute in Canberra on Wednesday.
Losing Mosul would be a major blow to IS as it is the largest city the group has held since leader Abu Bakr al-Baghdadi used the location to proclaim in mid-2014 a caliphate spanning Iraq and Syria.
Vice Admiral Johnston said the seizure of Mosul did not mark the end of IS in Iraq because there were still pockets flaring up from the city's west to the Syrian border and between Mosul and Baghdad.
He believes the Iraqi government understands the importance of reconciliation efforts between Sunni and Shia communities as well as accommodating the Kurds.
Earlier this month a couple of hundred US Marines deployed into Syria with heavy artillery guns as part of the ongoing preparation for the fight to oust IS from its self-declared headquarters of Raqqa.
Defence department boss Dennis Richardson said that in 2014, when IS shot to prominence, US and Australian military chiefs expected it would take three to five years to defeat.
That assessment was still on track.
He confirmed Australia had made both verbal and written input into the US Trump administration's yet-to-be-released new strategy to defeat IS.
While there is no talk of putting boots on the ground, the ongoing training role was important, he said.
"I think we need to be careful of pulling the plug too soon," he said.
"I see us continuing to be engaged in the Middle East ... for probably quite a while to come."
Australia has 780 defence personnel in Iraq and Syria, carrying out air strikes, special operations, and training Iraqi soldiers and police in the fight against IS.
There are also 270 Australian soldiers in Afghanistan.
