Washington: Flagging American public support for the Afghan war was a key factor in deciding to bring all 33,000 US surge troops home from Afghanistan by the end of next summer, Defence Secretary Robert Gates said.
The "advantages and disadvantages" of a range of options were debated in White House deliberations, including "not only the situation on the ground in Afghanistan but also political sustainability here at home," Gates said.
In an interview a day after US President Barack Obama`s announcement that he planned to pull out the 33,000 reinforcements by the end of September 2012, Gates said he was "comfortable" with the result and the discussions that preceded it.
The commander in Afghanistan, General David Petraeus, presented Obama with a range of options, but recommended a slower paced withdrawal, Gates said during the interview, which took place in his Pentagon office.
"Obviously he had preferred options that gave more time," Gates said.
The Pentagon chief said it was no surprise as top officers always want to have more boots on the ground.
"I would just say, both from my experience in this job and as a historian, I`m not aware of a single general ever in history that did not want more troops and more time," he said.
Military leaders had wanted to keep more forces in place through next summer`s fighting season to cement progress in the south and renew efforts in the east.
But Gates said all 33,000 reinforcements, who were ordered to Afghanistan in December 2009 to turn the tide in the war, will be withdrawn by "the end of September”.
Some lawmakers and commentators on the right have accused Obama of jeopardising gains against insurgents for purely political considerations before the US presidential vote in 2012.
But Gates, a 67-year-old Washington veteran and former CIA director who is retiring at the end of the month, defended Obama`s plan despite criticism that the timeline was arbitrary.
"I think these things are arbitrary to a certain extent, including the military timelines," he said.
"They`re a best estimate in terms of the military commanders, and they`re a best estimate in terms of the President`s desire for success in our mission in Afghanistan, which also requires political sustainability here at home."
Gates has often referred to a growing fatigue among Americans after years of war and amid rising fiscal pressures.
He said the decision did not represent a hasty exit, pointing out that while former president George W Bush withdrew his surge force in Iraq after a year, Obama will have kept reinforcements in place in Afghanistan for about two years.
Echoing Obama`s remarks on Wednesday, Gates said the reduced US presence would not alter what he called Washington`s "limited" goals in the war, reflecting a greater sense of "realism" after a strategy review in 2009.
Those goals, he said, are: to reverse the insurgents` momentum; deny them control of populated areas; degrade their capabilities; and bolster Afghan security forces to a point where they can prevent the overthrow of the Kabul government and the re-establishment of safe-havens for al Qaeda or other extremists.
"That`s it," he said.
Gates also said militant sanctuaries in neighbouring Pakistan remained a concern but that success in the war was possible even if Islamabad fails to fully cooperate in countering extremists along its border.
With Pakistan taking some positive steps, he said: "I think that as long as the picture stays mixed like that, that we can be successful."
He said that it was "not in the cards" for Pakistan to change its "strategic calculus" that focuses on India as an overriding threat.
Gates said the gradual drawdown plan would reassure European and other allies in the war, saying it gave them enough time to prepare.