Critics of President Biden’s decision to withdraw U.S. troops from Afghanistan warned that it sent the wrong message to the rest of the world. To our allies, they said, it signaled that we could no longer be trusted to honor our long-term commitments abroad; to our adversaries it showed that the United States had become a paper tiger whose threats they could safely ignore.

Now many critics of Biden’s policy in Afghanistan are worried that he is making a similar mistake in Ukraine by failing to respond firmly enough to the threat of a Russian invasion. Since 2014, when Russia annexed Crimea, Russian President Vladimir Putin has been fomenting a separatist insurgency in the Donbas, a largely Russian-speaking region in eastern Ukraine. At least 13,000 people have died in this simmering conflict. Last July Putin published a five-thousand-word essay in which he argued that Russians and Ukrainians are historically one people, not two, and accused the West of trying to drive the two countries apart. Since then, Russia has massed nearly a hundred thousand troops along its border with Ukraine, causing alarm not only in Kiev but also throughout Europe. No one in the West seems sure whether Putin is bluffing or preparing for a ground war, but Washington is taking no chances. On December 7 President Biden held a two-hour video meeting with Putin to express U.S. concerns about Russia’s troop movements. Biden warned that the United States would impose severe sanctions on Russia if it invaded Ukraine; he also discussed the possible terms of a settlement satisfactory to both Kiev and Moscow.

Biden’s critics, however, believe it is pointless to try negotiating with Russia. They say Putin has no right to demand that NATO officially disavow its 2008 resolution that Ukraine and Georgia would one day become members of the alliance. They also say that Putin would not be satisfied with the Donbas, that he has designs on other states on Russia’s western border, from the Baltic to the Balkans. Texas Congressman Michael McCaul, the top Republican on the House Foreign Affairs Committee, has urged the president not to offer any concessions to Russia. “This would not only fail to de-escalate tensions, it would also embolden Vladimir Putin and his fellow autocrats by demonstrating the United States will surrender in the face of saber-rattling,” McCaul told the New York Times. “Particularly in the aftermath of the disastrous withdrawal from Afghanistan...U.S. credibility from Kiev to Taipei cannot withstand another blow of this nature.”

But McCaul and other critics of the Biden administration are wrong. The solution to Russian saber-rattling is not American saber-rattling, and it would be foolish to try to shore up the credibility of the United States by risking an armed conflict with another nuclear power. Fortunately, there is a far better—and safer—solution at hand. But it will require that we apply pressure to both Russia and Ukraine. Both countries have been dragging their feet on the implementation of the 2015 Minsk II agreement, which was negotiated by the leaders of Russia, Ukraine, France, and Germany and endorsed by both the United States and the United Nations Security Council. That agreement would demilitarize the Donbas (Russian “volunteer” forces would have to withdraw from the area), restore Ukrainian sovereignty over the region and its borders, and grant full autonomy and language rights to the Donbas as part of a federal Ukrainian state. This last provision would require a constitutional change, which the Ukrainian government has so far been unwilling to make. Kiev fears that the Donbas might use permanent autonomy to keep Ukraine from joining NATO. For its part, Russia refuses to recognize Ukrainian sovereignty over the Donbas until the region’s autonomy is guaranteed. The United States should make it clear to Ukraine that NATO membership is not in the offing—two other member states, France and Germany, oppose it—and that if Kiev fails to abide by all the terms of Minsk II, the United States will cut off economic aid. Meanwhile, the Biden administration should let Putin know that if he tries to annex the Donbas, the United States will not hesitate to impose crippling sanctions on Russia’s banking system.

Until now, Washington has been leading Ukraine on—neither promising NATO membership nor ruling it out—while issuing stern but suspiciously cagey warnings to Russia. It is time to be clear and firm with both sides of this conflict, without pretending that the United States is about to fight World War III in defense of a territory that means much more to Russia than to us. Putin is a bad actor, an autocrat and a liar, but we should not be surprised if he—or any other Russian leader—does not want to see NATO expanded to Russia’s border, in clear violation of promises the United States made at the end of the Cold War. How would the United States respond if a rival world power tried to establish a military alliance with Mexico or Canada, or began training and supplying their soldiers close to our borders? Insofar as the confrontation in Ukraine is about American credibility, the United States cannot credibly demand of a rival what it would not tolerate for itself.