Afghanistan will need support from the West for up to 15 years, President Hamid Karzai warned Thursday ahead of a major international conference on his strife-torn country in London.

"With regard to training and equipping the Afghan security forces, five to 10 years will be enough," Karzai said in an interview with BBC radio.

"With regard to sustaining them until Afghanistan is financially able to provide for our forces, the time will be extended to 10 to 15 years."