A senior military official said Allen offered Defense Secretary Leon Panetta three plans, each with different troop levels -- 6,000, 10,000 and 20,000 -- and risk-factor probabilities, The New York Times reported Thursday.
The 6,000-troop option would probably pose the highest risk of failure for the U.S. effort in Afghanistan, the option with 10,000 troops would carry a medium risk and the 20,000-force option would be the lowest risk of the three, the official said.
However, the official told the Times the more important consideration in the success of any post-2014 U.S. mission in the Asian country depended on how well, or whether, the Afghan government could deliver basic services to its citizens.
The Obama administration recently has been considering the size and mission of a U.S. force that would remain after 2014 to help boost Afghan stability. Currently, about 66,000 U.S. troops are in Afghanistan.
Under an agreement between NATO and the Afghan government, the NATO combat mission ends Dec. 31, 2014, when the Afghan Army and police assume full responsibility for their country's security.