Karzai's statement Monday came as Pakistan released another group of Afghan Taliban prisoners, seen as a sign of the Pakistani government's willingness to help the United States and Afghanistan negotiate a peace agreement with the militants, Tribune Newspapers reported.
The Afghan government requested prisoner releases as a goodwill gesture.
The next stage for transferring security duties from NATO-led troops to Afghan soldiers and police will begin in two months and will give the Afghan forces the main responsibility for defending 87 percent of the population, Ashraf Ghani, head of an Afghan transition commission, said during a news conference.
Most coalition combat forces will be out of Afghanistan by the end of 2014.
Ghani dismissed concerns about the preparedness of Afghan troops to assume the lead against the Taliban-led insurgency, noting security has remained at least at the same level in areas where the shift in responsibility has been made, Tribune Newspapers said.
"When the enemies of Afghanistan have attacked the Afghan national security forces, they have been defeated," Defense Minister Bismullah Khan Mohammadi said during the briefing.
Officials with NATO's International Security Assistance Force said they expect Afghan forces to assume responsibility for the entire nation by the summer, with coalition troops in a support role.