A significant number of Australian troops will be home by the end of the year as the handover of security control to Afghan forces progresses, Australia's Defence Minister Stephen Smith says.

The Australian Defence Force's (ADF) 680-strong 3rd Battalion (3RAR) Task Group has already been replaced by the smaller 300-strong 7RAR Task Group, as the mission focus moves from mentoring and training to advising and supporting Afghan forces, the Australian Associated Press reports.

Smith told parliament on Thursday that based on the latest advice, security responsibility in Oruzgan Province would be fully shifted to the Afghan National Army (ANA) by the end of 2013.

"As transition proceeds there will be changes in the composition of the ADF commitment in Afghanistan," he said in an operations update.

"The overall number of ADF personnel will not substantially decrease until towards the end of 2013, as additional personnel are deployed temporarily to support the transition and redeployment effort."

As ADF withdrawals from patrol bases continues, the 16 Australian Light Armoured Vehicles (ASLAVs) will no longer be needed and will be returned to Australia.

However, 65 RAAF air defence troops are being deployed in Afghanistan to replace the Slovakian force, which provides security at the main multi-national base at Tarin Kowt.

The Afghanistan task group remained combat ready so it can assist the ANA if needed.

The Special Operations Task Group continued to conduct partnered combat operations to disrupt the insurgency.

Smith said the details of the fifth and final move to transfer security responsibility to Afghan forces would be announced soon.

He warned insurgent Taliban forces were expected to increasingly target Afghan security forces, using improvised explosive devices (IEDs) and high profile propaganda and insider attacks.

"As transition proceeds, Afghanistan will remain difficult and dangerous," Smith said.