But the Prime Minister, Julia Gillard, has told the Herald her government's decision to ''stay the course'' is reinforced by the views of the families of the slain.

''As Prime Minister, I've gone to a lot of funerals, I've spoken to a lot of families, I really understand the cost,'' she said.

''One of the things that amazes me when I do speak to families who have lost a loved one, when I do go to the funerals, is often they say to me that we best honour the sacrifice that they've made, and their loved ones have made, by staying the journey and seeing the mission through.''

Ms Gillard spoke to the Herald before the death on Monday of Sapper Rowan Robinson, 23, a combat engineer shot dead by insurgents while working with special forces troops in Helmand province.

The Australians and their Afghan allies had destroyed a huge cache of weapons and ammunition while under attack by insurgents. They then moved to a second location where they were attacked again and Sapper Robinson was shot.

He died later at the Australian base at Tarin Kowt.

Sapper Robinson was the 27th Australia soldier killed in the decade-long war and the fourth in a fortnight. Last week Lieutenant Marcus Case and Lance-Corporal Andrew Jones were killed in separate incidents.

On the same day their deaths were announced, the Victorian Liberal MP, Russell Broadbent, told the Coalition party room Australia should consider withdrawal.

''I believe there's been a tectonic shift in the mood of the Australian people,'' colleagues quoted him as saying.

Mr Broadbent, a moderate, said he supported continuing humanitarian support for the Afghan mission but not a military role. ''I believe now we should consider when we will be leaving,'' he said.

Mr Broadbent is the second Liberal MP to call for a withdrawal. Last October Mal Washer said Australia's original mission had been accomplished and it was time to leave.

Yesterday, the outgoing Chief of the Defence Force, Angus Houston, urged patience.

''Why would you pull out when you are making the best progress you have ever made?'' Air Chief Marshal Houston said.

''Why, why would you do it? We need to stay the course.''

Air Chief Marshal Houston said he could understand public unease about the war but was forceful when asked about whether Australia should consider withdrawing.

''I just don't think that's plausible. If we pull out immediately, we leave behind a very messy situation in the province of Oruzgan,'' he said.

The Opposition Leader, Tony Abbott, said yesterday was a ''hard and bitter day'' for Sapper Robinson's family but ''we need to understand that there is no such thing as casualty-free combat''.

Yesterday Ms Gillard said it was understandable that people were starting to ask, ''What are we doing there? Why are we still there? Should our soldiers be there?''

''I do want to say to people that this is not an endless war without a purpose,'' she said.

When Ms Gillard spoke to the Herald after the deaths of the two soldiers last week, she said the burden of casualties ''weighs heavily on me but the weight on me is nothing compared to the weight on the families that receive that news''.

''I do feel often very supported by the reactions I get from the families.

''You would well and truly understand that if someone spoke in anger and said 'why are we there?' or spoke in distress and said 'why did my son, why did my husband, have to go, why did they have to die?', I would understand that. But you don't tend to see those reactions.''

with Dan Oakes