These potential alternatives were produced by the Pentagon at the behest of the White House and reflect a familiar pattern within the US administration on the use of force. Sensitive to public opinion and budgetary pressures, the White House has generally favored lower troop levels during its previous deliberations on Afghanistan and Iraq.
The military, by contrast, has tended to favor somewhat higher numbers, because of the greater risks posed by a smaller force carrying out its mission in a rugged and hostile environment like Afghanistan. In this case, the Pentagon believes that the 9,000-troop option - the upper range of the new scale - is more realistic, officials said.
The new troop options were first reported Saturday by The Wall Street Journal, which said they would leave approximately 3,000, 6,000 or 9,000 troops in Afghanistan after 2014, when NATO nations are scheduled to hand over responsibility for security to the Afghans.
The Obama administration's deliberations over troops comes as Afghan president Hamid Karzai is preparing to visit Washington this week. The US and Afghanistan began talks in November on a possible pact that would authorise a US troop presence in Afghanistan after 2014.