Kerry, chairman of the powerful Senate Foreign Relations Committee, has been resistant to the addition of more troops into Afghanistan as requested by the US commander in Afghanistan, General Stanley McCrystal.
In an address to the Council on Foreign Relations on Monday, Kerry, who returned from Afghanistan last week, said, "We need to be extraordinarily way of over-extension. I am particularly concerned about the potential for us, ultimately to be viewed -- no matter how good our intentions and no matter what efforts we make -- as foreign occupiers."
He recalled that "riding around in an armed personnel carrier just the other day as I did when I was there, and seeing the faces through the window of Afghans watching that monster vehicles go by, you get a sense of the disconnect that Afghans must experience."
Kerry -- a highly decorated solider in the Vietnam war who strongly advocated against that war when he returned from Vietnam -- said, "it was an image that I recognise very well from 40 years ago -- a look, a stare, if you will -- that I came to know and understand."
"Look," he told the standing room only audience, "we are not the Soviets, we are not there to colonise, to conquer, to remake Afghanistan in our image, or to impose an ideology on is people. But it's just too easy for our well-intentioned presence to be misread, and for civilian casualties to stroke resentment and resistance."
Thus, he argued, the Obama administration "is right to be deeply concerned by the reality that as our footprint has increased, so has the number of insurgents."
In his conversations with General McChrystal, Kerry said "he understands the necessity of conducting a smart counter-insurgency in a limited geographic area. But I believe his current plan reaches too far, too fast."
"We do not yet have the critical guarantees of governance and of development capacity -- the other two legs of counter-insurgency -- and I have serious concerns about the ability to produce effective Afghan forces to partner with at the rate that we need to so that we can ensure that when our troops make heroic sacrifices, the benefits to the Afghans are actually clear and sustainable."
"With that in mind," Kerry said, "decisions about additional troops, should be best informed by an assessment that takes into account the following three conditions."
"First, are there enough reliable Afghan forces to partner with American troops, at what rate and eventually take over responsibility for security?"
Kerry said "the quickest way out of Afghanistan for our troops is to speed up the training and mentoring of the Afghan national army and police so that they can defend their own country."
He said the "second question to ask is, are there local leaders that we can partner with?" and emphasised that "the importance of that cannot be overstated. We have to be able to identify, cooperate with tribal, district and provincial leaders, who command the authority to help deliver services and restore Afghans's faith in their government."