A suicide bomber killed at least 10 people in Kabul on Saturday near a compound where Afghan elders will debate a security pact with the United States next week. Another 22 people were wounded.
A vehicle filled with explosives exploded 150 metres from a tent where about 2500 members of the Loya Jirga will gather on Thursday to decide the future of American troops in Afghanistan when NATO forces withdraw next year.
No group has said it carried out the attack.
The security pact governs the status of US military personnel staying in Afghanistan beyond the withdrawal of most international forces in 2014.
The BBC reports it must be approved by the Loya Jirga and parliament before it can come into force.
Earlier, President Hamid Karzai called on the Taliban and their allies to join the assembly.
"We invite them, please come to this national jirga of Afghanistan, raise your voice, raise your objection ... and share your views," he said in Kabul.
