KABUL, Afghanistan — The American campaign in Afghanistan has suffered a double blow: The Taliban broke off talks with the U.S., and President Hamid Karzai said NATO should pull out of rural areas and speed up the transfer of security responsibilities to Afghan forces nationwide in the wake of the killing of 16 civilians.

Thursday's moves represent new setbacks to America's strategy for ending the 10-year-old war at a time when support for the conflict is plummeting.