Barack Obama: 'We are working actively and diligently to consult with Nato'
US President Barack Obama stressed that the Afghan war was not purely an "American battle", as he met Nato leader Anders Fogh Rasmussen for talks.
Destroying al-Qaeda and building Afghan security were vital, he said, and the US would work with Nato "every step".
Mr Rasmussen - who had urged the US not to doubt its allies' commitment - said identifying the right strategy was key.
The meeting comes amid intense debate within the Obama administration over the way forward in Afghanistan.
On Saturday the top US general in Afghanistan, Stanley McChrystal, submitted a report requesting more troops and warning of failure should he be denied additional manpower.
But there are said to be divisions in the White House over any further deployment, amid a drop in public support for the operation.
Rising troop deaths and the chaos over last month's fraud-riddled election have contributed to the loss of confidence in the Afghan mission.
Speaking after talks at the White House, Mr Obama and Mr Rasmussen spoke of a joint effort in Afghanistan.
"This is not an American battle," Mr Obama said. "This is a Nato mission as well and we are working actively and diligently to consult with Nato at every step of the way."
OBAMA'S AFGHAN POLICY
Election campaign: Mr Obama says Afghanistan must be a priority and calls for more troops there, as well as political and economic progress
February 2009: Says he will send an extra 17,000 military personnel to Afghanistan this year
March: Announces an additional 4,000 US personnel will be deployed to help train Afghan police and army
May: Backs Defence Secretary Robert Gates as he removes the US commander in Afghanistan, Gen David McKiernan and appoints Gen Stanley McChrystal
August: Gen McChrystal warns Mr Obama in a report that the Afghan mission is likely to fail without more troops; urges a change in strategy to boost Afghan security forces and protect civilians
Sept: Gen McChrystal formally asks for more troops; the Pentagon says the request is on hold while the Obama White House decides its overall Afghan strategy
Mr Rasmussen, for his part, said that the alliance "will stand united and we will stay in Afghanistan as long as it takes to finish our job".
The Nato leader said he and other Nato members were studying Gen McChrystal's report - and he said he backed Mr Obama's approach of "strategy first, then resources".
"The first thing is not numbers," he said. "It is to find and fine-tune the right approach to implement the strategy already laid down."
The details of Gen McChrystal's report are not known, but analysts say he had been expected to submit a range of options from 10,000 additional troops up to 40,000.
The Obama administration is said to be torn between increasing troop numbers as requested or adopting a new strategy that prioritises crushing al-Qaeda over nation-building.
On Wednesday Mr Obama is to meet top security and defence advisers to discuss the way forward in the months ahead - the start of a series of discussions on the subject.
The White House says no decision will be made on troops until the strategy has been agreed.
There are currently around 100,000 foreign soldiers in Afghanistan from more than 40 countries. More than 60,000 of them are American.