The top U.S. military officer says the U.S. and Afghan troops must adjust as the Taliban shifts to more spectacular, high-profile attacks and assassinations.
Joint Chiefs Chairman Adm. Mike Mullen says commanders are working with the Afghans to shore up their personal security.
His comments came hours after a suicide bomber hiding explosives in his turban assassinated former Afghan President Burhanuddin Rabbani, who headed a government peace council trying to negotiate with Taliban insurgents.
Defense Secretary Leon Panetta says Rabbani was playing an important role in the reconciliation.
Panetta says he is hopeful that the U.S. will be able to work with others to continue the effort.