President Obama's envoy to Afghanistan has said winning the conflict there will be "much tougher" than in Iraq, BBC reported.
Richard Holbrooke told a conference in Munich: "I have never seen anything like the mess we have inherited."
At the same summit the architect of the US surge in Iraq, Gen David Petraeus, urged similar measures for Afghanistan.
General Petraeus warned that Afghanistan was likely to get harder before things improved, and called for a future change in tactics there.
The BBC's Rob Watson, at the security conference, says Gen Petraeus was clearly borrowing on lessons learned from Iraq.
In future US forces would live and work more closely with ordinary Afghans. More effort would be made to promote local reconciliation and good government, the general added.