US President Barack Obama has expressed concerns about the difficulty of maintaining a focused military mission in Afghanistan as his administration prepares a troop build-up there.
Mr Obama was addressing House of Representatives Democrats on the first day of a three-day retreat.
Following a speech that focused on the domestic economy, President Obama took questions during a short, private session.
Sources who were present at the closed session said Mr Obama was asked for his views on the Afghan situation.
The president responded that the US cannot win the war in Afghanistan by military means alone and a key danger for US forces is ‘mission creep without clear parameters.’
The sources, who asked not to be identified, said Mr Obama also told the House Democrats that Washington needs to engage in diplomatic efforts with Afghanistan's neighbour, Pakistan.
President Obama's remarks came on the eve of a trip by Vice President Joe Biden to Munich, where he is to meet with European leaders to consult with them about hot spots including Afghanistan.
The US has been waging a war against Taliban insurgents in Afghanistan since shortly after the 11 September 2001 attacks on New York city and Washington.
Mr Obama, just two weeks in the White House, is expected to approve up to 17,000 more combat troops for Afghanistan to help reverse a growing insurgency.
Barack Obama was elected in November in part on a pledge to pull US troops out of Iraq and devote more US military forces to Afghanistan.
During his remarks to the House Democrats, which were met with cheers according to those who attended, Mr Obama also said that Afghanistan cannot become a ‘safe haven’ for terrorists.
