KABUL, Afghanistan - Afghan President Hamid Karzai says his country's armed forces are taking over the lead for security around the country from the U.S.-led NATO coalition.

The handover of responsibility on Tuesday marks a significant milestone in the nearly 12-year war and marks a turning point for American and NATO military forces, which will now move entirely into a supporting role. It also opens the way for their full withdrawal in 18 months.

The handover was marred by a botched bomb attack against an Afghan politician in another part of Kabul. The bombing killed three civilians.