By Jessica Donati and Hamid Shalizi
KABUL, Nov 20 (Reuters) - The text of a U.S.-Afghan pact that sets out a blueprint for military cooperation after most foreign troops pull out next year was unfinished on Wednesday, a day before thousands of Afghan elders were due to start debating it.
Without the accord the United States has warned it could withdraw all of its troops by the end of 2014 and leave Afghan forces to fight alone against a Taliban-led insurgency.
The last-minute politicking between Kabul and Washington provoked frustration among Afghan elders who braved perilous journeys to the Afghan capital from remote provinces for a grand assembly to debate the pact.
"What is happening with the security pact is very confusing for us," said Abdul Hanan, a senator from the eastern province of Paktia, who will attend the gathering.
Last-ditch efforts to finalise the pact stalled on Tuesday over differences over whether President Barack Obama had agreed to issue a letter acknowledging mistakes made during the 12-year Afghan war.
"The final language is not ready between the two governments," said Aimal Faizi, the Afghan president's spokesman, adding the U.S. State Department was right to say that work remained to be done.
The Afghan government said it received assurances that an Obama letter would be provided this week to the grand council of Afghan elders, known as a Loya Jirga, which will consider the pact.
Susan Rice, Obama's national security adviser, insisted that such an offer - which would draw criticism from Republicans and anger American war veterans - was "not on the table".
The Taliban, fighting to expel foreign troops, have condemned the Loya Jirga as a farce. Security was tight in Kabul ahead of the meeting following a suicide bomb attack near the assembly ground over the weekend.
The security pact with the United States must be approved by the Loya Jirga that will meet for five days starting on Thursday.
If the two sides cannot agree on a pact, Afghan President Hamid Karzai has suggested submitting different versions of the document for the Loya Jirga to decide on.
That caused confusion among Loya Jirga members gathering in the capital, Kabul, ahead of the meeting's formal opening. Less than 24 hours before the start, attendees appeared deeply divided over the issue.
Khan Ali Rotman, who runs a Kabul-based youth organisation and is attending the grand assembly, said he would vote "yes" only if he believed it was good for Afghanistan.
"If it is not in line with our national interests we will raise our voice and not vote for it," he said.
A Kabul-based senator, Khan Mohammad Belaghi, said Afghanistan had no choice but to sign it.
"We have to have a partnership with a country like the United States and we will vote in favour of it because it can protect us from threats from neighbouring countries, especially Pakistan, and the Taliban," he said.
A security pact would clear the way for a decision on how many U.S. troops will stay in Afghanistan, where they will be based and what they can and can not do.
U.S. officials said during a meeting of NATO defence ministers in February that the alliance was considering keeping a residual force of 8,000 to 12,000 troops.
The United States and Iraq failed to reach agreement on a similar pact when the U.S. military mission there ended two years leading to a "zero option" outcome, or the withdrawal of all U.S. troops. (Editing by Maria Golovnina and Robert Birsel)