US President Barack Obama has said US and coalition forces will move to a support role in the Afghan conflict this spring.
Mr Obama said he will announce the next steps in the US troop drawdown in Afghanistan in coming months.
He was speaking during a news conference with Afghan President Hamid Karzai
This raises the prospect of an accelerated US withdrawal from the country and underscoring Mr Obama's determination to wind down a long, unpopular war.
President Karzai appeared to give ground in talks at the White House on US demands for immunity from prosecution for any US troops who stay in Afghanistan beyond 2014.
This concession could allow President Obama to keep at least a small residual force there.
Both leaders also threw their support behind tentative Afghan reconciliation efforts with Taliban insurgents.
They endorsed the establishment of a Taliban political office in Qatar in hopes of bringing insurgents to inter-Afghan talks.
Outwardly, at least, the meeting appeared to be something of a success for both men, who need to show their vastly different publics they are making progress in their goals for Afghanistan.
There were no signs of the friction that has frequently marked Mr Obama's relations with Mr Karzai.
President Karzai's visit came amid stepped-up deliberations in Washington over the size and scope of the US military role in Afghanistan once the NATO-led combat mission concludes at the end of next year.
The Obama administration has been considering a residual force of between 3,000 and 9,000 troops.
This is deemed far fewer than some US commanders propose to conduct counterterrorism operations and to train and assist Afghan forces.
But a top Obama aide said this week that the administration does not rule out a complete withdrawal after 2014.
This move is viewed by some experts as disastrous for the weak Afghan central government and its fledgling security apparatus.
Mr Obama left open the possibility of that so-called "zero option", when he several times used the word "if" to suggest that a post-2014 US presence was far from guaranteed.
Insisting that Afghan forces were "stepping up" faster than expected, Mr Obama said Afghan troops would take over the lead in combat missions across the country this spring, rather than waiting until the summer, as was originally planned.
There are some 66,000 US troops currently in Afghanistan.