Mohammad Hanif Sherzad, spokesman for Taliban leader Mullah Omar, told The Times of London on a satellite telephone: "Our activity will increase day by day. We now have the confidence to fight face-to-face and we have all the ammunition we need."
The spokesman also told The Times, "We will turn Afghanistan into a river of blood for the British."
The threat comes at a time when the Taliban reportedly has rearmed and recruited new followers to fight the 8,000-person NATO force from Britain, Canada and the Netherlands.
But Lt. Gen. David Richards, who will command the NATO forces, said he is not concerned about the threat and that his troops will "respond very robustly" if attacked.
The NATO deployment will allow the United States to reduce the number of its troops.