The Federal Opposition has questioned Prime Minister Julia Gillard's motives as she prepares to announce that most Australian soldiers will be pulled out of Afghanistan before the next election.

In a speech to be delivered to the Australian Strategic Policy Institute this lunchtime, Ms Gillard will lay out plans to pull troops out of Afghanistan a year earlier than originally planned.

Troops could start leaving as early as this year, with most troops home by the end of 2013.

A 2013 pull-out date will be a year in advance of the 2014 deadline previously laid down by NATO-led international forces, and will mean that the majority of troops are likely to be home before the next election.

But Defence Minister Stephen Smith has confirmed that some Australian soldiers, including special forces, will remain in Afghanistan after that date.

This morning Opposition acting defence spokesman George Brandis said he hoped the Prime Minister was not acting on purely political motivations.

"It would be a shameful thing if after nearly 12 years of deployment in Afghanistan and the loss of more than 30 Australian lives this mission were foreshortened for reasons of domestic political convenience for the Labor Party," he said.

The details will be hammered out at a crucial NATO meeting on Afghanistan in Chicago next month.

The Australian Government and other nations involved in Afghanistan have been saying the withdrawal will be a gradual process, and differ from region to region.

But in the Uruzgan region, where most of Australia's troops are deployed, officials believe the situation is better than anticipated, and the mentoring task is going successfully.

Ms Gillard will say she is confident that local forces are now ready to take control, despite the brazen attacks across Afghanistan in recent days.

However, any withdrawal still hinges on Afghan president Hamid Karzai declaring he is confident Afghan troops are ready to take control.

The Federal Government says it expects Mr Karzai to announce that Australian troops in Uruzgan will be withdrawn over an 18-month period.

Ms Gillard is also expected to outline a program of long-term financial and military support which will continue after the troops pull out.

Opposition Leader Tony Abbott said he would back the early withdrawal of Australian troops serving in Afghanistan if they had achieved success.

Mr Abbott said he believed it should be possible to "finish the job" in Afghanistan "sooner rather than later."

"I have been twice to Afghanistan, I have been lucky enough to talk to our senior commanders on the spot, to talk to our troops on the ground," he said.

"They think that they are doing very good work, they think that very significant progress has been made, is being made, will be made.

"We do have to respect their judgement."

Sorry, this video has expired Taliban attacks diplomatic targets in Kabul

Brazen attacks

The speech will come a day after Taliban squads launched brazen attacks in the heart of Kabul, sparking firefights which lasted for 18 hours, and leaving more than 50 people dead.

This morning Mr Karzai blamed NATO forces for what he said were intelligence failures which led to the attacks.

A total of 33 Australians have been killed while serving in Afghanistan: 32 with the Australian Defence Force, and one with the British Army.

Felix Sher, the father of Private Greg Sher who was killed in Afghanistan in January 2009, said he believed many lives had been improved by the international military presence.

"Unfortunately we've made this world into such a place that sometimes it takes a life to save a number of lives," he said.

"And I can only just pray that my son's life, like those of all other soldiers that have been sacrificed, will save multiples of their lives."

Mr Sher said he believed the decision had been taken for the best of motives.

"The Chief of the Defence Force David Hurley and the Defence Minister Stephen Smith would have made the decision based on knowledge and intelligence reports that they would have," he said.

"I have complete faith in their decisions and it's probably the right decision."

But former soldier Brett Shearer, who fought in Afghanistan in 2002, says returning troops will have mixed feelings about coming home.

"I suppose for the families it's probably a good thing," he said.

"Whether or not for the actual troops themselves, it depends on whether they feel the job has been done and they've done enough, whether they're going to be happy about coming home or not."

This morning retired Major General Jim Molan told ABC News Breakfast he was "a bit surprised to hear that we will be bringing out troops this year."

"We've got to wait until we hear exactly what the PM has had to say," he cautioned.

"The way it normally happens is that you transition and then you stay around: transition to local Afghan control of the province, and then for the initial period of time you stay around to act as a back stop to the Afghan forces just in case they stumble, as they inevitably will.

"And then you withdraw. I would hate to see a situation where we transition as we've got to do, and then immediately withdraw."

"So the detail is going to be very, very important to us assessing it."

New Greens leader Christine Milne demanded that Australians should be given the details of any agreement to be signed at the NATO talks in Chicago.

Calling Mr Karzai's government "a corrupt regime", Senator Milne said the war in Afghanistan had been a "failure on just about every level."

"From the Greens' point of view, it is time we brought the troops home safely," she said. "And we would like to see that withdrawal from Afghanistan start straight away."