Police 'key to Afghan stability'
Colin Powell says "real test" will be ability of Afghan police to protect civilians once fighting dies down.
Americans are being told to expect the war against the Taliban in Afghanistan to last well over another year.
The head of US Central Command, General David Petraeus, says the current operation in Marjah is only in its initial stages and the months ahead will be difficult. He was speaking on NBC's Meet The Press.
"They'll be tough. I have repeatedly said that these types of efforts are hard and they're hard all the time. I don't use words like optimist or pessimist I use realist but the reality is that it's hard and we're there for a very, very important reason and we can't forget that.
"We're in Afghanistan to ensure that it cannot once again be a sanctuary for the kind of attacks that were carried out on 9/11."
The tough talk comes as civilian casualties in Afghanistan mount. President Hamid Karzai has repeatedly asked Nato to protect civilians during combat operations.
The former US secretary of state, Colin Powell, spoke on rival CBS's Face The Nation.
Afterwards he told Al Jazeera that the Taliban is responsible for the deaths of most Afghan civilians but military and political leaders are well aware that ordinary Afghans are being caught in the crossfire.
"I think our military leaders and our political leaders and our military leaders in Afghanistan are very sensitive to it and they're doing everything they can to minimise that threat to the civilian population ... because at the end of the day they're the ones whose hearts and minds we're trying to win."
Questions remain about the transition from military operations to Afghan control - not least of all reconstructing the area once the fighting dies down.
The New York Times newspaper reports the Afghan military is far from ready to take on complex operations or act independently of Nato.
General Powell stressed the importance of the Afghan police when it comes to rebuilding.
"The real test, I think, is for the Afghan national police. They're the ones who will keep security in the region after the armies have moved out of the way. Armies fight people. Police protect people over the long-term and that I think is the real challenge in Afghanistan."
President Barack Obama's top commander in Afghanistan, General Stanley McChrystal, has spoken about delivering a "government in a box" to Marjah - by which he means a new governor, administrators and almost 2,000 police officers.
But in order to get to that point he knows Nato forces must first defeat the Taliban and keep civilian casualties to a minimum - something that may be easier said than done.