Paddy Ashdown said on Monday the biggest obstacle facing Bosnia was its poor economy.
"We should have began reconstructing the economy sooner," he said. He made the comments after talks in Berlin with German Foreign Minister Joschka Fischer.
Fischer promised Germany would continue to honour its obligations through this "difficult process" of getting the country back on its feet.
The effort includes helping with economic reconstruction as well as the capture of suspected war criminals.
Ashdown praised the European Union's role in helping Bosnia, hailed the "success story" of last year's parliamentary and presidential elections, and the repatriation of a million war refugees.
Up to 250,000 Muslims, Croats
and Serbs died in 1992-95 war
However, the country is still struggling to recover from three years of bloody war during 1992-95.
About 250,000 people died in the conflict between Bosnian Muslims, Croats and Serbs.
Since then, international administration has helped the country maintain a fragile peace, but ethnic tensions persist with crime and corruption flourishing.
Nearly half of the workforce is unemployed, the economy is moribund, and international aid is being reduced.
Moreover, almost two thirds of the country's young people are desperate to leave, according to a United Nations survey carried out in 2002.