The Loya Jirga, or Grand Assembly, descended into chaos on Thursday after an estimated 200 of the 502 delegates refused to vote on amendments to the draft charter, and counting of the assembly's first ballot was suspended.
The assembly will resume on Saturday, by which time interim leader Hamid Karzai and his supporters hope to have won over increasingly troublesome opponents seeking to dilute his powers ahead of presidential elections in June.
"Behind the scenes, I think there are negotiations between the leadership of the Loya Jirga and leaders of the opposition," said a member of the Constitutional Commission on Friday.
"They want to agree terms on certain articles." Leading the push for a stronger parliament are members of the Northern Alliance of mainly minority Tajiks who helped the United States topple the Taliban more than two years ago.
But now Washington's allegiance is firmly with Karzai, a pro-Western moderate from the majority Pashtun clan, widely seen as the only person capable of uniting his war-shattered country.
The centralised presidential system outlined in the draft is being challenged by smaller ethnic groups, including Tajiks, Uzbeks and Hazaras, who are also calling for official recognition of their languages and more power for provinces where they live.
"I am...concerned that there is an ethnic polarisation that
was unnecessary that could be, if allowed to continue, very
Francesc Vendrell, EU's envoy to Afghanistan
"This morning, delegates from the pro-parliamentary groups began meeting," Abd al-Hafiz Mansoor, one of the most outspoken critics of Karzai at the assembly, told reporters.
A UN spokesman said Afghan special envoy Lakhdar Brahimi was likely to be involved in talks on Friday.
Talks drag on
Saturday's session, if it takes place, will complete the third week of work at the giant white tent on a Kabul college campus, more than twice the 10 days set aside for the debate.
Afghan delegates queue to
register their voting
Karzai needs a simple majority to pass a version of the constitution suitable to him, but more walkouts by the Northern Alliance would badly damage the legitimacy of the process.
The fact that the standoff is broadly between Pashtuns, seeking a return to their traditional role at the centre of Afghan power, and smaller ethnic groups mostly living in the
north, has increased the stakes.
"I am...concerned that there is an ethnic polarisation that was unnecessary that could be, if allowed to continue, very damaging," the EU's envoy to Afghanistan Francesc Vendrell said on Thursday, adding that he hoped it was a "temporary explosion".