Nato's secretary-general has labelled the Afghan government as "ineffective", blaming it for the country's instability, reported Aljazeera .
Jaap de Hoop Scheffer said the main problem in Afghanistan was not the growing resurgence of the Taliban, but that the country had too little central control.
"Afghan leadership is not some distant aspiration - it's something that we need as soon as possible and on which we must insist," he wrote in an opinion piece in the Washington Post newspaper on Sunday.
The longer it takes to see progress, he said, the longer the military operation remains in place at a "real cost in lives".
"But we have paid enough, in blood and treasure, to demand that the Afghan government take more concrete and vigorous action to root out corruption and increase efficiency, even where that means difficult political choices."
De Hoop Scheffer also wrote that while Nato is obliged to keep ramping up the military operation, force alone cannot solve Afghanistan's problems.
His comments come as a suicide bombing in the capital Kabul killed at least five people on Saturday.
The Nato-led International Security Assistance Force in Afghanistan comprises about 55,000 troops from 41 contributing countries.