Australia is to start pulling troops out of Afghanistan this year and expects all international forces there to be playing a supporting role for Afghan forces by mid-2013.

Prime Minister Julia Gillard will present her timetable for withdrawal a year earlier than planned to the NATO conference on Afghanistan planned for Chicago in May.

"I am now confident that Chicago will recognise mid-2013 as a key milestone in the international strategy," said Australia's leader in a speech to the Australian Strategic Policy Institute in Canberra.

"A crucial point when the international forces will be able to move to a supporting role across all of Afghanistan."

All foreign combat troops are due to be out of Afghanistan by the end of 2014 and Australia had been expected to withdraw then too.

But U.S. President Barack Obama and other NATO leaders are expected to define more clearly Western withdrawal plans at the Chicago conference and outline measures to ensure Afghanistan does not collapse into civil war when foreign troops go home.

She has rejected suggestions the faster timetable was being driven by US President Barack and his desire to have withdrawal plans finalised before the November US presidential election, saying it was reliant on progress agreed by Afghan and international forces.

It comes after a major assault in Kabul by the Taliban this week which has raised questions about whether Afghan forces will be able to control security after foreign troops withdraw.

Gillard said she expected President Hamid Karzai to make an announcement on the transition in the coming months, and that it would take 12 to 18 months to complete the pull-out.