RENEE MONTAGNE, HOST:
NATO has promised a thorough investigation into the attack, which killed those 24 Pakistani soldiers. NPR's Pentagon correspondent Tom Bowman is on the line with the latest information. Good morning.
TOM BOWMAN, BYLINE: Good morning, Renee.
MONTAGNE: So, we've just heard a version of events from Pakistan. What are you hearing from your sources about what happened?
BOWMAN: Well, the Americans and Afghans are saying they were taking fire from the Pakistani side of the border, and they responded with attack helicopters and warplanes. Now, top U.S. leaders are - like Defense Secretary Leon Panetta and Secretary of State Hillary Clinton - they're offering condolences for any Pakistani deaths. And the Americans are now saying an investigation is under way to determine exactly what happened.
Now, I talked to one military official over in Kabul. He says it's really uncertain what happened here. He speculated that insurgents may have taken over some of these border posts, maybe co-opted the Pakistani forces. Or it was, maybe, just a tragic mistake. It's all very murky at this point, and will take some time to sort out.
MONTAGNE: You know, the attack took place just a day after NATO's top commander in Afghanistan met with Pakistan's top commander, to discuss better cooperation along the border. Is all of that work now undone?
BOWMAN: Renee, I wouldn't say undone, but it certainly has had a chilling effect. When something like this happens, you know, top-level meetings are canceled; cooperation among the military along the border can stop or slow; the trainers are thrown out; the U.S. is told not to use Pakistani bases. So, you know, various things can happen. We really don't know what will happen after this. But clearly, it's very, very serious.
MONTAGNE: Now, there have been cross-border attacks in this region before. We talk about them every once in a while. What's the difference here?
BOWMAN: Well, the scale is what's different here. You know, a year ago, the U.S. fired on and killed two Pakistani soldiers along the border. A joint investigation found that the Pakistanis fired first, but said they were firing warning shots. This, of course, is much more serious. You're looking at more than two dozen dead. So we'll just have to see what happens with that investigation.
MONTAGNE: And Tom, we've heard just now about some of Pakistan's responses to this latest attack. What more details can you give us? What, exactly, might be the impact on U.S. operations in Afghanistan?
BOWMAN: Well, the biggest impact is closing those two border crossings. The U.S. relies on these to get food and fuel and building materials into Afghanistan. But again, this has been done in the past. They've closed these border crossings a number of times. They've really become something of a political football. And as a result, over the past number of years, the U.S. has opened up a new supply route that comes from Europe through Central Asia.
About half of all supplies now come along that route. And the U.S. would like to beef it up to about 75 percent. And one of the reasons is because, you know, the relationship with Pakistan is so unstable.
MONTAGNE: OK. Then finally, let's take a step back here. How much of a setback do you see - or do your sources at the Pentagon see to an already tense relationship between Pakistan and the U.S., especially when it comes to military cooperation?
BOWMAN: Well, you know, one of the things, you know, when something like this happens you could, again, have slowing of military cooperation between the U.S. and Pakistanis. I think there's a concern about that. There is a lot of coordination along the border. So the real worry is to lose that cooperation along the border. But again, we'll just have to wait and see what happens. But people are very, very tense about this latest situation.
MONTAGNE: NPR's Pentagon correspondent Tom Bowman, thanks very much.
BOWMAN: You're welcome, Renee. Transcript provided by NPR, Copyright National Public Radio.