Taliban fighters in recent months have been increasing the number and intensity of their attacks on NATO convoys that pass through Pakistan.
Several bold attacks in recent weeks have targeted not just trucks, but also a key terminal near Peshawar where trucks and cargos are kept before making the final part of their journey into Afghanistan.
Those attacks have focused international attention on NATO's so-called "Lines of Communication" project with Russia and former Soviet republics in Central Asia.
But NATO spokesman James Appathurai has downplayed the significance of the attacks on NATO's supply system.
"First of all, it's not that dangerous. These [attacks] are high-profile events. But they are, from what I understand from the military, statistically and strategically insignificant if you look at the bulk of the logistics effort," Appathurai tells RFE/RL.
"They are of concern. But they basically make no statistical difference to the supplies going into that country," he says. "But of course, the Taliban in that region is trying to undermine logistics to that area to the extent that they can."
Appathurai says NATO's interest in building alternative overland supply routes into Afghanistan can be dated back more than two years -- long before the Taliban started targeting convoys and cargo terminals.
"My understanding is that these discussions are going quite well. They are supported by the Russian Federation. Is there any change in the last few months? No. I think they are going forward," he says. "We always hope for them to go forward more quickly. But I understand that there are no political problems. Only technical ones. And those are being addressed."New Routes Needed
There currently are about 65,000 foreign troops in Afghanistan -- including soldiers in the NATO-led International Security Assistance Force as well as U.S.-led coalition forces.
About 75 percent of the supplies for those foreign troops -- military equipment, food, fuel and other vital provisions -- arrive from the West by ship at the Pakistani port of Karachi. From there, those supplies are loaded onto trucks and driven hundreds of miles across Pakistan to cargo terminals on the outskirts of Peshawar. Finally, convoys of trucks carry the supplies into Afghanistan through the Khyber Pass.
Matthew Clements, the Eurasia analyst at the London-based publication "Jane's Country Risk," says he agrees that the amount of NATO supplies destroyed in Pakistan by the Taliban in recent months has been insignificant compared to the total amount of supplies moving through that route.
"It wasn't a large percentage," Clements says. "However, the theory is that if these attacks continue on this sort of scale and become more regular, it is going to impact on the supplies reaching NATO forces. Hence, I think there is a genuine concern within NATO of the need to diversify its [supply routes]."
Clements has been closely following developments on possible alternative supply routes. He notes that Russia and Uzbekistan both signed an accord with NATO in April that calls for cooperation on delivery of supplies into Afghanistan.
"They've been in discussions and there was an agreement indeed signed at the April  NATO summit in Bucharest between Russia and Uzbekistan with NATO for the overland delivery of supplies to NATO forces [in Afghanistan]," Clements says.
"This would be nonlethal military supplies, so obviously not ammunition or war machines, etc. It would be more like food and fuel and these kind of things. Now, this was signed although it still has not been implemented. And little progress has been made on it," he adds. "Obviously, some damage was done to any progress by the downturn in relations between Russia and the West -- especially following the August conflict between Russia and Georgia."
Overland Through Russia
Clements also says that Moscow, despite its disagreements with the West over the conflict in Georgia and the U.S. missile-defense shield, continues to pledge support for NATO operations in Afghanistan because it is in Russia's best interest, as it realizes "the risks that [failure in Afghanistan] could pose to its own southern borders and also the risk posed by the expanding drug production and exports from [Afghanistan.]"
"There are a number of options [for alternative overland supply routes] on the table. But I think [NATO] would bring supplies to the Baltics. The access to ports is quite important. So to the Baltics and then through Russia, and overland through mainland Europe [into Russia] as well. These are all possible options," Clements says.
"Russia does offer the most direct overland route from Europe -- and across, obviously the Black Sea or the Caspian Sea and through Central Asia to Afghanistan," he adds. "Russia also has a more advanced infrastructure than the Caucasus or Central Asia."
But Clements says other supply routes are possible that would not pass through Russia -- including a Caucasus route with supplies arriving from the Black Sea and moving across the Caspian Sea into Central Asia -- perhaps with Turkmenistan or with Uzbekistan's involvement.
However, he notes that the situation "has changed quite a lot in recent years. Obviously, the [use by U.S. forces of an air base] was closed by Uzbekistan following the harsh criticism [by Washington] of its actions in Andijon. But I think since then that Uzbekistan has become slightly frustrated with the fact that its turning toward Russia hasn't received quite what it thought it would do. I think [Uzbekistan] has realized that there is an opening again for U.S. influence and for U.S. aid. And it has opened itself up to a degree.
"But at the moment, it still remains fairly embryonic, and few other details have emerged on what could happen. I certainly haven't seen anything suggesting there would be a reopening of an air base," he says. "But it does show that Uzbekistan is open to more cooperation with NATO and the United States."
Clements says Turkmenistan also has become a more feasible option since the death of President Saparmurat Niyazov in 2006, as "the new administration has opened itself up -- not just to the West but also to Russia and China. And it is seeking to expand its best relations," he says.
"One of the things it has put forward is a kind of opening toward the United States and Western aid and investment," Clements adds. "And a part of this could obviously be through military cooperation -- although, again, this does remain embryonic, and no concrete deals have been put forward in terms of bases or overland [supply] routes."
Clements concludes that it is the lack of transport infrastructure in Central Asia and the Caucasus that is the biggest hurdle to overland supply routes through those regions.
He says there needs to be a lot of investment in the restoration of old railroads and highways, and the building of new ones. That means it could take years and millions of dollars before a reliable alternative overland supply route can be established for NATO forces in Afghanistan.
RFE/RL's Uzbek Service contributed to this report