US Secretary of State Hillary Clinton has warned Taliban fighters in Afghanistan that they face a stark choice between war and peace, as US military pressure on them mounts.
"They cannot defeat us. And they cannot escape this choice," Mrs Clinton said in a speech in New York.
The US plans to begin withdrawing troops from Afghanistan this summer, with full withdrawal expected by 2014.
Currently, the US has about 78,000 troops there.
Mrs Clinton also announced that retired diplomat Marc Grossman would replace the late Richard Holbrooke as chief US envoy to Pakistan and Afghanistan.
Speaking at the Asia Society research organisation, Mrs Clinton reiterated US's three-track strategy in Afghanistan: a military offensive against al-Qaeda and the Taliban; a civilian-led effort to strengthen the Afghan and Pakistani governments, economies and civil societies; and a diplomatic effort to end the Afghan war.
She said the US aimed to bolster an Afghan-led effort to split the Taliban from its al-Qaeda allies and reconcile those willing to renounce violence with the Kabul government.
"In 2001, after 9/11, the Taliban chose to defy the international community and protect al-Qaeda," she said.
"That was the wrong choice, and they have paid a heavy price. Today, the escalating pressure of our military campaign is sharpening a similar decision for the Taliban: break ties with al-Qaeda, give up your arms, and abide by the Afghan constitution and you can rejoin Afghan society; refuse and you will continue to face the consequences of being tied to al-Qaeda as an enemy of the international community."
US forces are expecting heavy fighting to resume this spring after the annual winter lull.
But Mrs Clinton said that the security situation had improved and begun to stabilise, with gains made "at the village level".
"The momentum of the Taliban insurgents has been blunted and in some places even reversed," she said.
She said al-Qaeda remained a "serious threat", but said the US had given the group's allies and sympathisers reason to question the value of the alliance.
Meanwhile, the US government has said it is imposing sanctions against 16 groups and individuals in Afghanistan for allegedly laundering money for drug traffickers.
They include the New Ansari Exchange, which is thought to be the biggest of Afghanistan's money-transfer firms. The group, which has affiliates in Dubai, is accused by the US of laundering money from heroin, opium and morphine trafficking in Afghanistan.
Washington said that those on the list would have their assets in the US frozen, and US citizens would be banned from doing business with them.