Maj. Gen. Robert Cone, who is in charge of equipping and training Afghan security forces to take over from international troops, said the local units were making good progress, but declined to say when they would be strong enough to allow foreign forces to go home.
Violence is soaring in Afghanistan despite years of counter-insurgency operations by international troops and millions of dollars spent in equipping the country's army and police units.
Cone cautioned that military force alone would likely not be enough to beat the Taliban and other militants battling foreign and Afghan government troops.
"You can say you defeated them in a single campaign ... but again given the complex nature of this environment, they might be back again the very next year," he told a media conference in the capital Kabul. "I think the real issue is probably not a military solution in the long term."
Afghan President Hamid Karzai earlier this year said he had met with unspecified Taliban militants in an attempt to reach a political settlement, but did not elaborate on the extent of the contacts.
Cone, who arrived in Afghanistan in July, said the "military will have a significant impact on the overall solution, but in reality most insurgencies are dealt with by political solution in the end."
Hundreds of former members of the hard-line Taliban regime, including a sprinkling of former senior commanders and officials, have reconciled with the government since they were ousted from power in the U.S.-led invasion in 2001.
But current rebel leaders have apparently refused to hold talks, and over the past year, thousands more fighters have picked up guns and joined the insurgency, which this year alone has left more than 3,900 people dead.
Formal talks with the Taliban would be politically very sensitive because of the close relationship top commanders are believed to have with al-Qaida leaders, including Osama bin Laden.
In the latest violence, unidentified assailants Thursday killed a NATO soldier and wounded two others in a routine patrol in southern Afghanistan, the alliance said in a statement. An Afghan interpreter working with the troops also was killed, the statement said. NATO did not provide the soldier's nationality or the circumstances that lead to the deaths.
On Wednesday, Afghan soldiers and coalition forces found and destroyed an insurgent-run drug lab after a brief fight in restive Helmand Province, according to a statement. The opium lab was the second of its kind found in the past four days in the province.