ARUN RATH, HOST:

Afghanistan finally has a new president after months of political instability. Ashraf Ghani was sworn in on Monday. And on Tuesday, he signed a bilateral security agreement with the United States. That will allow nearly 10,000 U.S. troops to remain in the country past he end of this year to support the Afghan army in the continuing fight against the Taliban.

Meanwhile across the border, the Pakistani army continues what's been called a major offensive against the Pakistani Taliban that began over the summer. Christine Fair teaches at Georgetown University. She believes the U.S. and Pakistan face a conflict of interest when it comes to fighting the Taliban on both sides of the border. And Fair is skeptical of taking the Pakistani army's war with the Taliban at face value.

CHRISTINE FAIR: So I don't like to call it a war on the Pakistani Taliban, because that's not really what it is. What the Army is trying to do - and you can sort of see immediately the conflict of interest for the United States - is that they're basically trying to take elements of the Pakistan Taliban organization and split them into those militants that can be persuaded to go to Afghanistan, where they are intended to kill us and our allies, and those elements of the Pakistani Taliban that want to continue fighting the Pakistanis.

And the reason for that is the United States has a supreme interest in Pakistani stability. The Pakistanis are very good at exploiting this idea of the Islamist barbarians at the nuclear gate to coerce the United States to help Pakistan on its terms.

RATH: So then what does this mean for the fighting across the border in Afghanistan against the Taliban there?

FAIR: The fighting in Afghanistan is going to continue. And Pakistan is really hoping for this. Because as soon as there is no hope for the Afghan Taliban to regain power, all of these militant groups that Pakistan has dispatched to Afghanistan will have no reason to keep fighting.

RATH: So given all of that, what kind of an ally do you expect Pakistan to be as the U.S. draws down its troop levels in Afghanistan now through 2016?

FAIR: Our interests are so deeply conflicted. The fact is that the Americans needed the Pakistanis because of the logistical requirements to continue funding the war in Afghanistan. And so from the beginning of this conflict, you had a supreme conflict of interest in the sense that the very organizations that we were trying to defeat in the country were in fact those very organizations that Pakistan viewed as its ally.

RATH: So is the Taliban the victor? Who wins in Afghanistan?

FAIR: Well, I mean, ultimately the Pakistanis win. Let me caveat that. Even though the American troop presence is going to continue to withdraw, we still have this fundamental issue of whether or not the U.S. Congress - and ultimately it's going to be the Americans that continue footing the bill, not any of our other NATO/ISAF partners.

So the only thing that keeps the ultimate Pakistan/Taliban victory at bay is the American willingness to keep writing these bills. And I'm going to say it very bluntly - in perpetuity. Throughout this entire conflict, no one has even remotely considered a way of making Afghanistan economically sustainable. All we've done is focused upon troops - how many, where should they be and what should they do?

And this means that the American taxpayer is going to be paying. And until we stop paying, this whole thing begins to crumble.

RATH: Christine Fair is an assistant professor at Georgetown University and the author of "Fighting To The End: The Pakistan Army's Way Of War." Transcript provided by NPR, Copyright NPR.