The new US commander in Afghanistan has outlined a major change of strategy to improve security in areas where Taleban guerrillas continue to operate.
US troops are involved in a major operation against Taleban fighters
General David Barno said US bases would be set up in the south-east, where the violence has forced international aid agencies to pull out.
He said the move would also open the way for landmark elections next year.
His comment came as Afghanistan's grand assembly appeared to have made progress on agreeing key constitutional issues.
Delegates at the loya jirga debating the country's draft constitution reportedly agreed in principle to back a strong presidential system supported by Afghan interim President Hamid Karzai.
General Barno said that by March next year there would be at least 12 civilian-military units - Provisional Reconstruction Teams (PRT) - operating in Afghanistan, including deployments in the troubled regions of Zabul and Oruzgan.
He said he anticipated a hostile reaction from insurgents but was determined to implement his plan.
General Barno told the Associated Press news agency that insurgents would "realise that's the death knell to terrorist organisations in that part of the country".
The spate of recent attacks have forced the UN and other relief agencies to leave some areas, seriously affecting aid delivery.
The attacks have also threatened to undermine the reconstruction efforts by the US-backed Afghan Government.
So far, the nine PRT units have been operating in relatively secure regions of Afghanistan.
Boost for Karzai
On Saturday, the US envoy to Afghanistan, Zalmay Khalilzad, said it appeared that President Karzai was winning support for the controversial presidential system after a week of debates at the loya jirga.
The loya jirga is forging Afghanistan's political future
"At this stage it looks like there is a preference for a presidential system," Mr Khalilzad told reporters.
The issue has proved to be one of the most divisive issues for some 500 delegates at the loya jirga.
Some mujahideen - fighters who fought against the Soviet Union - have been particularly opposed to the idea of a strong president, preferring instead to have a prime minister or parliament with real teeth.
On Saturday, President Karzai repeated that he would only stand in the elections if the assembly approves the presidential system.