"We can send more troops. We can kill or capture all the Taliban and al-Qaida leaders we can find, and we should. We can clear out havens and shut down the narcotics trade. But until we prove capable, with the help of our allies and Afghan partners, of safeguarding the population, we will never know a peaceful, prosperous Afghanistan," the Joint Chiefs chairman, Adm Mike Mullen, wrote in a newspaper column.

Mullen also said that US forces have to gain the trust of the people in Afghanistan. The insurgency won't ever end if US forces accidentally kill civilians in the country or give people reasons to think badly of the United States, according to Mullen's column posted on The Washington Post's Web site on Sunday and set to be published on Monday.

"That's why images of prisoner maltreatment at Abu Ghraib still serve as recruiting tools for al-Qaida," Mullen said.

"And it's why each civilian casualty for which we are even remotely responsible sets back our efforts to gain the confidence of the Afghan people months, if not years."