* Talk of total U.S. withdrawal after 2014 alarmed Afghans
* "Zero option" seen by some as negotiating tactic
* No top commanders were asked for advice - NATO source
Top military planners on the NATO-led mission in Afghanistan were not asked to give their views on the possibility of all U.S. troops being pulled out of the country after 2014, a senior NATO officer said on Thursday.
The fact that top planners have not been asked for input suggests the so-called "zero option" might not be being looked at seriously by U.S. President Barack Obama's administration.
Analysts have said that the U.S. administration may have floated the idea as a tactic to put pressure on Afghan President Hamid Karzai while the two sides negotiate over the future U.S. military presence in Afghanistan, including issues such as whether foreign soldiers would be immune from prosecution.
"We have not been asked to or been required to provide a conversation (advice) with respect to the zero option," the NATO officer said, briefing reporters on condition of anonymity.
Asked about the "zero option" last week, U.S. Deputy National Security Adviser Ben Rhodes said it was "an option that we would consider", contradicting the long-held expectation that thousands would remain to train and advise Afghan forces.
Alarmed Afghan lawmakers said disaster and civil war would follow if Washington pulled out all of its troops.
There are some 66,000 U.S. troops in Afghanistan. The U.S. and other foreign forces there are gradually reducing their troops as Afghan forces take charge of the nation's security.
General John Allen, the top U.S. and NATO commander in Afghanistan, has suggested keeping between 6,000 and 15,000 U.S. troops in Afghanistan after 2014, according to U.S. officials.
The White House has asked recently also for options to be developed for keeping a lower range of troops, between 3,000 and 9,000, in the country, officials said.
The senior NATO officer said on Thursday he expected firm numbers on the size of the post-2014 mission in Afghanistan to emerge "within a couple of months" and that many of the numbers quoted by media "have not been accurately reported".
"It is less about a particular number than it is about how well that mission can be executed at a particular number," the officer said.
The United States expects other NATO allies to contribute in addition between a third and a half of the number of troops that Washington decides to leave in Afghanistan after 2014, he said.
"In the post-2014 period, whatever the U.S. number is, add a third of that or a half to that," he said.
The number of bases that the post-2014 force will operate from would be cut back sharply, the officer said.
"(We) have about 226 bases remaining in Afghanistan that we have to close over the remaining 23 months and that number varies because we are closing bases every day - as fast as we can actually," the officer said.
The post-2014 force would be likely to operate out of Bagram airfield near Kabul, retain offices in the Afghan capital, and have staff at the Afghan military training centres, he said.
Depending on the size of the force, it could have advisers in key Afghan regions or could employ mobile training teams, going from one Afghan regional headquarters to another, he said.