By CNN's Elise Labott and Shirley Henry
Editor's note: This is one in a series of stories and opinion pieces surrounding the Aspen Security Forum currently taking place in Aspen, Colorado. Security Clearance is a media sponsor of the event, which is taking place from July 17 to 20 in Aspen, Colorado.
The former commander of U.S. and international forces in Afghanistan, retired Gen. John Allen, cautioned Friday against leaving no U.S. troops in Afghanistan after 2014.
Speaking Friday at the Aspen Security Forum, Allen said that although the Afghan army has made great gains, Afghan leaders realize its forces are not fully trained and need a U.S. presence beyond next year.
"I've got a good bit of experience with senior Afghan leaders, and I can tell you almost to a person, they desperately want our presence after this war," he said. "They don't want us in large numbers, but they want us there in enough numbers to help to continue to develop the ANSF (Afghan National Security Forces)."
Allen, who retired in April, said he was never asked to evaluate a "zero option" - leaving no U.S. troops behind after 2014 - but added that if that option is in play now, it's "largely out of exasperation with the rhetoric coming out of the palace," referring to the strained U.S relationship with Afghan President Hamid Karzai.
Senior U.S. officials have said recently that President Barack Obama was considering the zero option. Until now, U.S. and Afghan officials had been discussing plans to keep a small force behind to fight insurgents and train Afghan security personnel, but the precise size of that force has yet to be determined.
Karzai has said he would like for U.S. troops to remain after the end of the NATO mission. But he also has been highly critical of those troops over the years, following incidents in which U.S. forces have killed civilians.
The relationship between Obama and Karzai further soured last month after the United States and the Taliban planned peace talks. In response, Karzai cut off negotiations with the United States on the residual troop presence post-2014.
If the United States pulls out all its troops, it will be a situation similar to what occurred in Iraq.
The refusal by the Iraqi government to extend legal protections for U.S. troops after the end of the war in Iraq was a major reason the United States left the country with no residual military training force.
Speaking at the Aspen forum Friday, Ambassador Paul Bremmer, the former head of the Coalition Provisional Authority in Iraq after the 2003 U.S.-led invasion, said that pulling all U.S. troops out of Iraq at the end of 2011 was a "mistake" and warned against pulling out of Afghanistan too soon.
Former Ambassador to Pakistan Husain Haqqani told the audience that talk of a zero option sends the wrong signal to the Taliban that they can eventually regain power in Afghanistan.
"There is a perception around the world that Americans don't lose wars, they lose interest," Haqqani said. "Telling them the date of when you are leaving tells them how long they have to wait."