* Contradicts Kerry's statement of "one issue" outstanding
* Failure to reach a deal could prompt U.S. pullout
* Afghanistan not in a hurry, but optimistic - spokesman
* U.S. request for nine bases approved by government (Adds estimate of deal deadline)
By Hamid Shalizi and Jessica Donati
KABUL, Oct 21 (Reuters) - Afghanistan and the United States have not yet agreed on several issues in a bilateral security pact, a senior Afghan spokesman said, raising the prospect that Washington may yet pull out all of its troops next year unless differences are ironed out.
Two years ago, the United States ended its military mission in Iraq with a similar "zero option" outcome after the failure of talks with Baghdad.
For almost a year, Washington and Kabul have been seeking to conclude a Bilateral Security Agreement (BSA) that will help determine how many U.S. soldiers and bases remain in Afghanistan after most foreign combat troops exit by the end of next year.
U.S. Secretary of State John Kerry told reporters at the end of a visit to Kabul this month that there was just one issue outstanding - Washington's demand that its troops be immune from Afghan law and tried in the United States instead.
But this request was not even raised in the two days Kerry was in Kabul, said Aimal Faizi, the spokesman for Afghan President Hamid Karzai.
"A lot of progress has been made on the document, but it is not finalised," Faizi told Reuters in an interview at the presidential palace.
"If we do not reach a final agreement on this draft, it will go to the Loya Jirga and the Afghan people will be able to look at the issues remaining." Faizi said. "If it's unfinished, it means that there are some areas even the two governments have not yet reached an agreement on."
The Loya Jirga, an assembly of tribal elders, is to meet in November to discuss the security agreement.
U.S. President Barack Obama's administration however regards the language hammered out during Kerry's visit as final.
"The text that will be presented to the Loya Jirga is what we left Afghanistan with on Saturday (Oct. 12)," U.S. State Department spokeswoman Jen Psaki told reporters last week.
U.S. officials are increasingly impatient to conclude the deal because they need time to implement plans for 2015. Washington wanted it done by the summer and most recently set an Oct. 31 deadline, but there is now no chance of a deal until late November.
A senior U.S. strategist in Kabul working on plans for 2015 said every month that passes will make it harder to get the troops and funding requested in time. That said, as long as the BSA was passed by the Loya Jirga at the end of November, the time-frame would still be manageable.
The "drop-dead date" for signing the deal was February, he estimated, adding that this could be why the Afghan government was resisting pressure.
"The president has said this previously. We are not in a hurry to sign this document. If not finalised, this could continue with the next government," Faizi said.
"There are some key issues still remaining but it is not really a lot of work," he added, indicating a deal could be reached before the presidential elections in April. Karzai cannot run because he has already served the maximum two terms.
U.S. officials insist that a security agreement is in both countries' interest but say the Obama administration is not bluffing about resorting to the "zero option" if American troops are not granted immunity from Afghan prosecution.
Other outstanding differences include the issue of unilateral U.S. military operations which have long infuriated Karzai. He has said they violate Afghan sovereignty, previous agreements and inflict terrible casualties on civilians.
While progress had been made in this area, Faizi said, it remained unresolved. Afghanistan is refusing to let the United States take unilateral military action even in retaliation against an attack.
"The Afghan government, as the host country, will take action," Faizi said. "The U.S. will not have the right to retaliate unilaterally if U.S. forces or bases are attacked. We are against all kinds of unilateral military operations."
Other issues included the ways in which the United States would continue to build and equip the Afghan security forces, and how many bases the U.S. would be allowed to retain.
"We have the U.S. asking for nine military bases, to which the government of Afghanistan has agreed. So now, it is up to the people in the Loya Jirga to decide if they want less or more," Faizi said.
That said, one major difference had been resolved - an Afghan request for protection from external aggression, something the U.S. had been reluctant to agree to, in case it required offensive action against another ally, Pakistan.
"The definition that we have for aggression - which both sides have agreed on - is much better than before ... We can say that we reached a kind of agreement," Faizi said.
U.S. officials said Kerry and Karzai had resolved differences over the wording of the guarantee but offered only a vague explanation of what had been agreed.
U.S. officials are largely optimistic about the chances that the security pact will win approval from the Loya Jirga, and Defense Secretary Chuck Hagel said on Monday that progress toward an agreement was "on track".
However, Washington is concerned that as campaigning for the Afghan election intensifies, it will be harder to broker a deal.
The NATO-led force in Afghanistan is hoping for a credible handover before most troops are pulled out at the end of next year. (Additional reporting by Matt Spetalnick, David Alexander and Lesley Wroughton in Washington and Phil Stewart in Brussels.; Editing by Christopher Wilson and Nick Macfie)