Pakistan’s suspension of U.S. military supply routes has highlighted the increasing importance of ex-Soviet countries, most notably Uzbekistan and Russia, to the United States’ war effort in Afghanistan. But there are also signs that those countries may not be as reliable as the U.S. would hope for, auguring a difficult next few years for America as it manages these seemingly delicate relationships.

The latest round of trouble with Pakistan began November 26, when a U.S. air attack killed 24 Pakistani soldiers just over the border from Afghanistan. Pakistan immediately announced that it would boot the United States from an air base that the Americans had been using to launch drones against militant targets in Pakistan’s north, and also that it would shut its border with Afghanistan to NATO military traffic. Islamabad also pulled out of a meeting in Bonn on December 5 that the United States wanted to use to bolster regional cooperation in advance of the 2014 start of the U.S. and NATO withdrawal.

The U.S. and NATO, having already anticipated problems with Pakistan, had been building up another set of overland supply routes from Europe through the former Soviet Union to Afghanistan, known as the Northern Distribution Network (NDN). By the time of the Pakistan cutoff, a bit more than a third of NATO cargo to Afghanistan went in via the northern route, slightly more than via Pakistan. The remainder goes in by air, which avoids any geopolitical complications but is far more expensive.

It's not known how long Pakistan will keep the supply routes closed, but after an incident last year in which the U.S. killed three Pakistani soldiers, Pakistan shut off the border for ten days. U.S. officials say that with the NDN, and with large amounts of goods stockpiled in Afghanistan, they don't anticipate any shortages as a result. Still, recent events have shown that the United States’ partners on the northern route may now try to take advantage of its increased dependence on them.

Uzbekistan has been a key partner on the NDN and an estimated 98 percent of overland traffic from the north to Afghanistan passes through the southern Uzbekistan border city of Termez. As a result, and despite the unseemliness of cooperating with one of the most brutal and repressive governments in the world, the United States has been strengthening its ties with Tashkent. Washington recently changed its policy which forbade sales of military equipment to the country because of its miserable human rights record. Secretary of State Hillary Clinton, on a visit to Tashkent in October, said there had been “progress” on human rights and democracy in the country, prompting critics to claim that Washington was selling out its principles for the sake of access for its military.

Thus far, the tradeoff has paid off: Uzbekistan has been a solid partner on the NDN. But recently, there have been signs it may not be willing to go along with all of the United States’ Afghanistan plans. Uzbekistan has, without explanation, abstained from the recent U.S. push for regional cooperation among Afghanistan’s neighbors. While Pakistan's pullout from the Bonn meeting garnered headlines, Uzbekistan skipped both that meeting and an earlier one on the same topic, in Istanbul in November.

A mysterious explosion at a railway bridge on the Uzbekistan-Afghanistan border also has raised suspicions that Uzbekistan may be using the NDN as leverage in its own power plays. The November 17 blast was described as a “terrorist act” by the Uzbekistan authorities, raising the specter of Islamist terror groups infiltrating Uzbekistan to punish the country for its cooperation with the U.S. in Afghanistan.

But since then, the picture of what happened at the bridge has become much less clear. It has emerged that the explosion, though very near a route that the U.S. used to ship cargo to Afghanistan, didn’t in fact interfere with that transit. It did, however, interrupt traffic to Tajikistan, Uzbekistan’s neighbor to the southeast. The two countries have had chronically poor relations, and Tajikistan, isolated by huge mountains, depends on Uzbekistan for rail access to the rest of the world. Uzbekistan has previously cut off rail transport to Tajikistan, and officials from Tajikistan have complained that Uzbekistan is taking much longer to fix the bridge than necessary, has given them no information about the incident and has declined Tajikistan’s offers of help.

That behavior has given rise to suspicion, in Tajikistan and abroad, that Uzbekistan may have engineered the blast itself. Two possible motives have emerged: Tajikistan had been seeking to gain some NDN traffic – and the accompanying transit fees – for itself, and Uzbekistan may have wanted to nip that effort in the bud. Secondly, there was a clash between border guards of Uzbekistan and Tajikistan a few days before the explosion, in which the Tajik side killed an Uzbekistan guard, after which Uzbekistan publicly threatened Tajikistan.

While both those theories sound conspiratorial, the fact that Uzbekistan hasn’t released any information about the incident has only fueled suspicion that there’s something to hide. And if Uzbekistan is willing to destroy its own infrastructure to tweak a neighbor (and possibly interfere with a potential NDN route), this surely raises questions in the Pentagon about how reliable a partner Uzbekistan can be.

To add to the Pentagon’s headaches, Russia’s NATO ambassador, Dmitry Rogozin, then announced that Russia may suspend its cooperation on the NDN if the U.S. doesn’t compromise on its European missile defense plans. Russia isn’t as essential a link as Uzbekistan – the coalition can bypass Russia by transiting through the Caucasus, across the Caspian Sea into Kazakhstan and then Uzbekistan. But the Russian route is nevertheless easier and cheaper.

Both Uzbekistan and Russia benefit financially from the NDN, through transit fees and local business generated. And both benefit from the coalition’s suppression of Islamist militants who, were they not pinned down by the U.S. and NATO in Afghanistan, could spread northward into Central Asia toward Russia. So ultimately, neither country has an interest in disrupting the war effort.

At the same time, however, both countries know that the United States is depending on them for transit to Afghanistan. And so it should be expected that they’ll try to elicit concessions from the U.S. on issues that are important to them: limiting missile defense in Russia’s case, isolating Tajikistan and reducing pressure to reform its political system in Uzbekistan’s. So while America’s military logistics planners can probably rest assured the NDN will keep humming, its diplomats will likely have a busy few years keeping these difficult partners satisfied.