“The jirga delegates will endorse what the government tells them to endorse,” said Jawed Kohistani, a political analyst. The jirga’s deliberations are broken down into 50 committees, he said, each headed by a government loyalist. The only way the jirga is likely to say no to a security agreement with the Americans, he said, is if Mr. Karzai wants it to say no.

Aimal Faizi, Mr. Karzai’s spokesman, disagrees, saying that the jirga organizers cast a wide net, sending out some 3,000 invitations. There are 2,500 attendees. All members of Parliament and local government officials down to the district level were among the invitees, as well as representatives of the Taliban — who did not come — and other opponents of the president, some of whom did. Most mainstream opposition figures, however, either were not invited or boycotted the event.

In his opening speech, Mr. Karzai encouraged the delegates to vote their consciences. “I want you to make your decision independently,” he said. “Whoever comes to you and claims to be my representative, don’t believe them.”