The forces hunting Osama bin Laden and Taliban leader Mullah Mohammad Omar say the two are thought to be hiding in the mountains around Kandahar or Jalabad.
The Taliban is hemmed in to a shrinking corner by nearly eight weeks of US bombing and ground Northern Alliance offensives.
It now also faces hundreds of US marines pouring into a remote desert airstrip in striking distance of the militia's last stronghold, Kandahar.
"They [bin Laden and Mullah Omar] are alive and still in Afghanistan," spokesman Mr Mohammad Habeel said.
He said the two men could be hiding either in the Safi Koh mountains near the eastern city of Jalalabad or the jagged ranges around Kandahar, the last city still in Taliban hands.
In Washington, a Defense Department official said the thrust of the US military campaign was now to sever the Taliban and al-Qaeda chain of command to encourage their fighters to give up.
"If we break the leadership of the Taliban and break the leadership of al-Qaeda, there is reduced motivation for troops to stay loyal to the cause and continue to fight," Rear Admiral John Stufflebeem told reporters.
He said leaders of the Taliban and al-Qaeda were finding it harder to communicate with their soldiers.
CBS Evening Newsreported several senior Taliban officials, including the head of military intelligence and at least two government ministers, had defected to the Northern Alliance and were now in Pakistan.
There was no immediate confirmation of the report from the Alliance or the Pakistani government.
Taliban leader Mullah Omar has urged his forces to stand and fight as reports of defections suggested his fundamentalist Muslim movement might be crumbling.
"Don't vacate any areas," said Mullah Omar in a radio message. "This is not a question of tribes. This is a question of Islam".