During an interview with a private Afghan television channel, Karzai said that initial investigations into the assassination Rabbani have pointed out that individuals from Quetta were behind the killing and that a fact-finding delegation will travel to Pakistan soon to investigate the case.
"The findings of our national security agencies reveal that the those behind the killing are in Quetta. If Islamabad does not cooperate we have no other option but to refer the case to the US for investigations," Karzai added.
The Afghan government has set up an investigation commission to investigate the killing of Rabbani. Afghanistan's defence and interior ministers, the chief of national directorate of security and the attorney general office are members of the commission.
Karzai indirectly warned Pakistan and said, "Initial reports show some foreign hand is involved. But if the Taliban is behind this killing then there is no need continue the peace negotiations with them."
"The Taliban killed our men in the battlefield but still the peace process was kept going. They even killed my brother (Ahmed Wali Karzai). But in case of Rabbani, they first took responsibility for the assassination and then retracted," he said.
"If they call themselves messengers of peace and then kill the person, who is leading peace process on behalf of the government how can they (Taliban) claim they want peace in Afghanistan? If really the Taliban have killed him, then who are we reconciling with? If Taliban is not behind we should trace the actual killer," Karzai added.