One unintended consequence of Russia’s invasion of Ukraine is the dramatic impact on Finnish and Swedish threat perceptions. Although both countries are strong and capable NATO partners who have contributed to alliance missions in the Balkans, Kosovo, Afghanistan, and Iraq, Helsinki and Stockholm have maintained a policy of military non-alignment in foreign affairs. Until the war in Ukraine, a majority of public opinion in both countries supported this posture. Today, however, more than half of Finns and Swedes support joining NATO and the Finnish prime minister has indicated that a decision to apply for membership could come by June. For his part, NATO secretary-general Jens Stoltenberg noted that he expected “all allies to welcome” Finland and Sweden if they applied since “they could easily join this alliance.”

Yet, despite the shift in Finnish and Swedish attitudes towards NATO membership, U.S. policymakers should be opposed to expanding security responsibilities that would cement a neo-Cold War stand-off in Europe.

The emergence of competitive multipolarity means that a “new strategic conservatism,” Charles Kupchan, a senior fellow at the Council on Foreign Relations, recently explained, requires “avoiding the further extension of defense commitments” into the Russian and Chinese “rimlands.” Material limits on the United States’ ability to wield its power abroad and the demonstrated willingness of other great powers to defend their spheres of influence should reinforce this perspective among U.S. foreign policy elites. Unfortunately, it is one that U.S. diplomats repeatedly dismissed during their engagements with Russian officials to avert a war in Ukraine. Instead, the Biden administration chose to uphold NATO’s open-door policy on principle rather than accommodate concrete geopolitical realities.

Preventing a “new Cold War” with Moscow will require avoiding this mistake a second time around when considering NATO membership for Finland and Sweden. To be sure, there are important differences between Finland and Sweden, and Ukraine and Georgia. The two Nordic countries have advanced and well-equipped militaries that maintain a high degree of interoperability with NATO systems and command structures. Additionally, both countries have low levels of corruption and no active territorial conflicts or disputes. However, while Finland and Sweden would likely make good NATO members, incorporating them into the alliance will exacerbate risks that offset the potential for improving security in the Baltic Sea region.

More specifically, strategic stability would not be served by eliminating the last neutral buffer zone between the West and Russia. Some commentators contend that enlarging NATO to include Finland and Sweden will strengthen the alliance’s eastern flank and sharpen deterrence in the Baltic Sea region. Russia’s defensive posture would then have to account for another Western-aligned neighbor with security guarantees, making a preemptive attack against the Baltic states more dangerous and costly.

But Russia has made it clear that it will not quietly acquiesce to a revision of the status quo in the Baltic Sea region. Dmitry Medvedev, the former president and current deputy chairman of the Security Council, warned Finland and Sweden that “it would not be possible to talk any more about the Baltic non-nuclear status. The balance has to be restored.” Additionally, Russia would have to “seriously reinforce its group of ground forces and air defenses and deploy significant naval forces in the Gulf of Finland.”

To be clear, stationing nuclear weapons in the Baltic Sea region would not alter the strategic balance in Russia’s favor and, in fact, they might already be deployed there. As the Lithuanian defense minister noted last week, “Nuclear weapons have always been kept in Kaliningrad … the international community, the countries in the region, are perfectly aware of this.” Yet, the issue is not whether Russia will attempt to achieve nuclear superiority but if it will enhance the role of nuclear weapons in its strategic doctrine and lower the threshold for their use to compensate for greater conventional inferiority against NATO. After the collapse of the Soviet Union, for example, Russian nuclear doctrine allowed that nuclear first use would be permissible to include local and regional conflicts. When the war in Ukraine ends, it would not be surprising to see Russia engage in more aggressive signaling as a response to further NATO enlargement on its northwestern border. Even though the risk of conflict will remain low, cavalier references to nuclear use will increase threat perceptions in NATO capitals and make responsible efforts to pursue détente and crisis management even more challenging.

Another concern is whether NATO allies can contribute to making the 830-mile-long Finnish-Russian border more defensible. While the Biden administration has deployed thousands of additional rotational troops to eastern Europe, given its prioritization of China as a “pacing threat,” permanent regional force posture increases will not be forthcoming. It is also unlikely that other NATO members will have the spare resources to make up the difference, particularly in Finland which has no natural barriers on its land border with Russia and, during a contingency, would need to be quickly reinforced using vulnerable maritime transit routes in the Baltic Sea. Again, even though it is unlikely that Russia will launch a preemptive attack against Finland, it would be irresponsible for NATO to extend security guarantees that it does not have the capacity to fulfill. Indeed, strategic overstretch will weaken the credibility of the Article V mutual defense mechanism. A European-led consolidation and reinforcement of NATO’s peripheral members, not territorial growth, should be the order of the day.

Tensions between the United States and Russia are at their highest point since the 1962 Cuban Missile Crisis. The urge to punish Russia for its unprovoked and unjustified war in Ukraine has led some commentators to deem it “poetic justice” that a conflict started to thwart Ukrainian ascension into NATO could lead to an enlargement of the alliance. This perspective does not embody a careful consideration of what best suits U.S. national interests. Pushing NATO closer to Russia’s border will only exacerbate Moscow’s pervasive sense of insecurity and elevate its threat perceptions. Worse, enlargement to include Finland and Sweden will cement a neo-Cold War posture in Europe that intensifies great-power rivalry while burdening the United States with more security responsibilities in a region of secondary importance. This time around, the Biden administration should state publicly that it will oppose NATO membership for Finland and Sweden.

Matthew Mai is an editorial intern at The National Interest and a senior at Rutgers University.

Image: Reuters.