"The number of Taliban mujahidin who are ready to launch the spring battle has reached 6000," Mullah Dadullah told the Kabul bureau chief of Al Jazeera's Arabic channel.
Dadullah said that the fighters were concealed in tunnels and elsewhere in preparation for launching their attack.
He said he might even be able to deploy even more volunteers if Nato troop increases continued to prompt more Afghans to take up arms. "It may rise to 10,000," he said.
Special forces
Australia currently has about 500 in Afghanistan working with Dutch Nato forces in Uruzgan province.
Australian special forces commandos were withdrawn from Afghanistan last September, but The Australian newspaper said Australia would send about 250 special forces troops back to the country, as well as extra helicopter support.
Nelson said while Australia had not yet made a formal decision to deploy extra troops to Afghanistan, he had discussed the issue with the Netherlands, British and US governments and Australians should not be surprised if extra troops were sent.
Before they were withdrawn, Australia's special forces spent 12 months in Afghanistan, where they were involved in long-range missions to hunt down Taliban fighters.
At the time, Australia's defence force commander left open the option of sending the special forces back to Afghanistan but said they first needed a rest.