The Taliban claimed responsibility for a blast on Monday that the US military said killed four soldiers. The Taliban said nine Americans were killed and US forces were helpless in the face of such attacks.
"Taliban attacks will further increase with a decrease in the winter cold," a former Taliban governor of Kandahar province, Mullah Mohammad Hassan Rahmani, told Reuters by satellite telephone from an undisclosed location on Tuesday.
Fighting in Afghanistan traditionally eases off during the winter when mountain passes get blocked by snow.
But violence has surged in recent months, including 15 suicide blasts since November, as Nato members led by Britain, Canada and the Netherlands prepare to expand their peace-keeping mission.
At the same time, the US is hoping to withdraw about 3000 of the more than 18,000 troops it has in a separate force battling the insurgency.
US military officials say the Taliban have changed tactics since suffering heavy losses in clashes early last summer, and are now increasingly using roadside bombs and suicide blasts against soft targets.
Nato is planning to expand its
But Rahmani said the Taliban had grown stronger since they were expelled by US and Afghan opposition forces after the 11 September 2001 attacks, and the suicide bombers were helping to drive US forces out.
"American forces have become helpless before the Taliban's suicide and other attacks," he said.
"The Taliban are inflicting heavy losses on American forces in men and material and it is to hide the cowardice and failure of their troops that America is reducing its forces."
The deployment of about 3300 British troops in southern Afghanistan later this year would give the Taliban more targets to attack, he said.
"An increase in foreign forces in Afghanistan will provide the Taliban easy targets and make it easier for them to attack and inflict losses," Rahmani said.
British forces are going to be stationed in Helmand province, while the Dutch will be in Uruzgan, where the US soldiers were killed on Monday.
Canada will soon have about 2000 soldiers in Kandahar, another insurgent hot spot in the south.
Most Afghans say they need foreign troops in their country to ensure security.