United States-Russian military tensions are exploding. On June 23 the Pentagon announced plans to station hundreds of tanks, howitzers and other armor in the Baltics and throughout other East European NATO countries. Russia meanwhile is increasing its forces in Belarus and speeding up the deployment of Iskander missiles to Kaliningrad, the heavily armed Russian exclave between Poland and Lithuania.

While both the United States and Russia should step back from the brink, many Obama administration officials are pushing for a dangerous escalatory step: the shipment of billions of dollars of lethal weapons to the post-Maidan government in Ukraine.

The lobbying to arm Ukraine began in February when three of the nation’s leading think tanks released a widely-read report arguing for the United States to provide Ukraine with $3 billion of lethal arms. Since then both the Senate and House passed legislation calling for the United States to arm Ukraine, while Secretary of State Kerry, Secretary of Defense Ashton Carter and U.S. Air Force General and NATO Supreme Allied Commander Philip Breedlove publicly advocated this policy. In fact, the only senior official not pushing this agenda is President Barack Obama — though the pressure on him to do so is growing.

Washington’s legion of escalation argues for “raising the costs” to Russia by increasing the number of Russian soldiers killed in Ukraine. The Kremlin has been hiding the number of battlefield casualties in Ukraine from Russian citizens to reduce domestic opposition to the war. If the volume of casualties became public, some U.S. officials argue, Putin would have to back down from Ukraine to prevent a domestic backlash.

This rationale is logical on its face, but in practice does not account for the gap between the Russian and American stake in Ukraine. Kiev’s geopolitical orientation is supremely important to Russia, while American interests’ via-a-vis Ukraine are peripheral at best. It’s a case of “must have” for the Russians, versus “nice to have” for the United States.

If Putin’s sky-high approval ratings are anything to go by, he has successfully convinced Russia’s citizens that Ukraine is an existential issue for their country, and he cannot now retreat without undermining his political standing at home. Therefore, Putin’s likely response to an increase in Kiev’s military capabilities would be to double down on his support for the separatists. In a worst-case scenario, Russia could invade Ukraine outright. The end result would be even greater death and suffering for those living in eastern Ukraine — the exact opposite outcome that the West would like to see.

Those who still doubt Russia’s willingness to escalate should consider what happened in August, when Ukraine’s military was on the brink of routing the separatists. Putin poured Russian troops into the Donbass and inflicted a bloody defeat on the Ukrainian forces at Ilovaisk. Russian troops also played a key role helping to defeat Kiev’s forces at Debaltseve in February. These incidents show that Putin is prepared to escalate as necessary, and the “Arm Ukraine” advocates do not provide a satisfactory explanation why he would not do so again.

Russia’s geopolitical interest in Ukraine is also matched by hard power. The Russian military possesses what military strategists call “escalation dominance,” and even those in favor of arming Ukraine admit that an American-supplied Ukrainian army still cannot defeat a determined attack by the Russian military. If Kiev appears on the verge of another significant defeat, do those demanding Ukraine be armed stand down? Or do they invoke “American credibility” and demand even tougher countermeasures? How might Moscow escalate even further in return? None of the answers to these questions are clear — and neither is the endgame.

Those who support arming Kiev also overlook the possibility that Putin could choose to escalate asymmetrically, outside of Ukraine. Russia already announced its intention to begin supplying Iran with advanced surface-to-air S-300 missiles by 2016. Moscow has promised this before, but then backed down, and Putin has left himself some wiggle room by saying Moscow won’t deliver S-300s to Iran “in the near future.”

However, if the United States arms Ukraine, Putin could accelerate the delivery of S-300s to Iran, and perhaps the even more lethal S-400s as well. These missile systems would make it much harder for the United States or its allies to carry out air strikes against Iranian nuclear facilities, for example. Acquiring advanced weapons would strengthen the position held by Iranian hard-liners who oppose a nuclear deal with the West.

Putin also recently hinted that Russia could supply S-300s to the Assad regime in Syria. Israel would naturally worry about these systems ending up in the hands of Hezbollah, a close Assad ally and sworn enemy of Israel. A jittery Jerusalem might launch a pre-emptive strike before the S-300s are even out of their crates, and events would spiral down from there.

If Putin wants to hit the “rogue regime trifecta” Russia could expand its relationship with North Korea. Moscow and Pyongyang already announced their intentions to deepen economic and political ties under the banner of a “year of friendship.” With the pariah Kim regime determined to expand its nuclear arsenal, anything that reduces North Korea’s isolation is inimical to American interests.

Finally, there is the issue of “blowback.”

Last July, poorly trained Russian-backed separatists allegedly shot down a commercial airliner with a Russian-supplied Buk anti-aircraft missile, killing all 283 people onboard. Meanwhile, numerous privately-funded battalions fight for the post-Maidan government. Although they are nominally under the government’s control, some of the most controversial battalions — such as Azov — warn they could “bring the war to Kiev” if conditions in Ukraine do not improve.

This raises a frightening question: What if American military hardware sent to Ukraine ends up in the wrong hands? We’ve seen this story before. In the 1980s the United States supplied advanced Stinger anti-aircraft missiles and other arms to the Afghan mujahedeen fighting the Soviet occupation. When the Soviets withdrew from Afghanistan, the United States packed its bags and went home — but its military equipment stayed behind.

When the Soviets’ puppet regime collapsed in 1992, the country was left in the hands of warlords and armed groups. Some reports indicate that these American Stingers ended up as far afield as Iran, North Korea and Libya, while others disclosed that al Qaeda ended up with advanced American sniper rifles.

More recently, Islamic State has reportedly seized “significant quantities” of American-made weapons from Iraqi government forces and moderate Syrian rebels. As the United States engages in an ongoing campaign to degrade and destroy Islamic State, the American military must now confront its own weapons. Ukraine is certainly more stable than Afghanistan, Iraq or Syria, but as history demonstrates American military aid sometimes goes missing.

While the United States should provide Ukraine political and economic support, shipping billions of dollars in lethal arms is just too risky.