KABUL, Jan 3: Afghanistan's constitutional debate, which has exposed deep ethnic divisions and challenged the US vision of a strong presidency, is just "one word" away from being wrapped up, officials said on Saturday.

But the whole process would collapse if delegates failed to reach a deal on the country's post-Taliban charter by the end of Sunday, they warned.

The Loya Jirga, or Grand Assembly, is entering its fourth week, more than double the time allotted, and has been marred by a boycott from voting on Thursday by nearly half the 502 delegates at the giant white tent on a Kabul college campus.

"If tomorrow we cannot finalize it (the constitution) we will announce to the world that we have failed," said Sibghatullah Mojaddidi, chairman of the assembly. "We are stuck on one word."

Delegates said that word was "Uzbek", and whether the Uzbek language should be recognized as official alongside Pashto and Dari, spoken by Tajiks.

The debate has effectively been suspended since Thursday, with behind-the-scenes deals taking up Friday and Saturday.

The scale of the protest has already forced some concessions from supporters of interim leader Hamid Karzai, who insists on a strong mandate to hold his country together as he heads into elections scheduled to take place in June.

And it has underlined deep-seated suspicions between Pakhtoons and smaller groups like the Tajiks, Uzbeks and Hazaras.

Private talks were expected to continue until late into the evening as they had done the night before, with the United Nations and United States acting as mediators.

The row over the recognition of a third state language is part of a broader clash between Karzai's backers and leaders of the Northern Alliance of mainly Tajiks, led by former president Burhanuddin Rabbani and Uzbek strongman Abdul Rashid Dostum.

Mr Karzai's opponents want to dilute his powers and bolster those of parliament and the provinces, and some members of the alliance favour a stricter interpretation of Islamic laws than does the more religiously moderate president.

A Western diplomat said Karzai had been forced to give some ground, including making the president "responsible" before parliament and ministers open to censure by lawmakers.

"The presidential system has already been watered down," he said on the sidelines of the meeting.

Several delegates openly criticized Mr Karzai and his ministers for trying to force through the draft constitution.

"These ministers are the main cause of the problems today and why we have been so long at this Loya Jirga," said Abdul Rauf Mokhles, a university professor from the western city of Herat.

"They are playing a dangerous game and they are playing it rather badly," added a Western observer.

A deal has been reached to hold parliamentary elections within six months of a presidential vote, not within a year as in the draft. There has been disagreement on around 20 of the 160 articles, but open voting and debate have been largely prevented.-Reuters