Secretary of State Mike Pompeo has informed his Russian counterpart, Sergei Lavrov, that any future agreement on nuclear-arms control between the US and Russia must also include China. This shift to trilateral negotiations is part of the Trump administration’s effort to remake great-power arms control for a new era. It’s a reasonable approach, which accurately holds that the old bilateral formula has become disconnected from reality. Whether the US can build the leverage necessary to make this new approach succeed — particularly vis-à-vis China — is far less certain. The Donald Trump administration, in pursuing this strategy, is breaking with two prior arms control paradigms. The Cold War model focused on stabilizing the competition between Moscow and Washington by capping the size of their nuclear arsenals and limiting their pursuit of the most destabilizing systems. The post-Cold War approach focused on cleaning up the strategic residue of the superpower conflict — namely, by reducing US and Russian arsenals. The most recent such agreement was New Start, signed in 2010. That pact trimmed the number of deployed strategic nuclear warheads to roughly 1,550 on either side; it limited the US and Russia alike to 700 deployed intercontinental ballistic missiles, submarine-launched ballistic missiles and nuclear-capable heavy bombers. Over time, however, two developments degraded the strategic value of the second paradigm. First, the Russians stopped honoring key agreements, while also carrying out a major nuclear-modernization program. In 2018, the Department of Defense reported that Moscow was violating several nuclear and conventional arms control pacts. Most important was the Intermediate-Range Nuclear Forces Treaty of 1988, which Russia broke by developing and deploying ground-launched missiles of a prohibited range. This left the US as the only country in the world that was effectively constrained from building ground-launched missiles — conventional or nuclear-tipped — with a range between 500 and 5,500 kilometers. After the Barack Obama administration spent several years trying to bring Moscow back into compliance, the Trump administration withdrew from the treaty last year. Second, the old approach ignored the rise of China. Since Beijing was not a party to the INF Treaty, it was free to assemble a fearsome arsenal of intermediate-range missiles to target US bases, ships and allies in the Western Pacific. Washington, as part of the agreement with Russia, was unable to respond by deploying such missiles of its own. As the US reduced its nuclear inventory, moreover, China began to build up its comparatively modest arsenal. In 2019, the head of the US Defense Intelligence Agency observed that Beijing “is likely to at least double the size of its nuclear stockpile” over the next decade. The US increasingly found that existing control agreements did not correspond to a changing strategic situation — and even weakened its position vis-à-vis Beijing. Pompeo’s recent remarks hint at the administration’s response to this problem. By withdrawing from the INF Treaty, the administration has sought to free the US from agreements that inhibit its ability to compete with Russia or China. By signaling that it expects future agreements to be trilateral, the administration is serving notice that it will no longer give China a free pass. And by recommitting to a major nuclear modernization program that dates back to the Obama administration — while also pursuing innovations such as lower-yield nuclear weapons meant to strengthen the credibility of the American deterrent — the administration is trying to build the pressure that might allow for more advantageous arms control deals in the future. Before the US can build down, in other words, it will have to build up. There is some sound strategic logic here. It makes little sense to forever gear the US arms control agenda to the challenge posed by Russia when China is now the primary competitor. Although both Russia and China are improving their nuclear arsenals, neither presumably wants a prolonged strategic competition with an unconstrained, economically superior US. Withdrawal from the INF Treaty was not as damaging to the unity of NATO as some observers feared at the time; there are early signs that US allies in the Asia-Pacific might eventually be willing to host INF-range missiles (probably conventional rather than nuclear). Most important, the Trump administration’s approach reflects an understanding of the paradoxical logic of arms control — that intensifying an arms race is often a precondition to de-escalating it on favorable terms. Nonetheless, the administration faces some real challenges. For one, China currently has little reason to enter a trilateral agreement on either intercontinental or intermediate-range systems, precisely because it enjoys many of the benefits of arms control with few of the liabilities. The US could, over time, give China a reason to cooperate, by showing that its position will worsen as America deploys INF-range systems in the Asia-Pacific and modernizes its own arsenal. Unfortunately, the US modernization program has been delayed repeatedly, and its future seems uncertain given the potential for COVID-19 to devastate the defense budget as it has devastated the economy. If Trump or a future Democratic president comes to see the US arsenal as a source of budgetary savings, America may end up lacking the leverage needed to force its competitors to the table. Second, a trilateral framework brings dangers as well as advantages. That format might allow Washington to subtly drive a wedge between Russia and China, by reminding Moscow that the nuclear domain is virtually the only area in which it is still superior to Beijing. Yet that format might also create opportunities for two US rivals to gang up on Washington in the negotiations, a ploy Russia and Iran seem to have run in the talks leading to the 2015 agreement on Tehran’s nuclear program. One way or another, managing three-way negotiations will require intricate, disciplined diplomacy, a task to which Trump isn’t well-suited. A third challenge relates to the nearer-term decision on whether to extend the expiring New Start with Russia for another five years, until 2026. Russian President Vladimir Putin has said he is willing to do so; the Trump administration has so far refused to commit. The calculation may be that holding out increases US diplomatic leverage over Moscow, while allowing US to establish the principle that future negotiations must shift to a three-way format with China. Yet it isn’t entirely clear who would benefit if the treaty actually lapses. In theory, both sides would then be free to build beyond New Start’s limits. In practice, both sides would face constraints. Russia has a head start, in the sense that its missile production lines are already hot. But Moscow is also experiencing a severe cash crunch from collapsing oil prices in addition to pre-existing economic stagnation: These trends will hamper its modernization or force sharp trade-offs against other priorities sooner or later. The US has far greater economic capacity, but its modernization program will not gather real momentum until well into the 2020s or even the 2030s, assuming it isn’t set back further by post-coronavirus fiscal austerity. Over the long term, an intensified arms race surely favors the US In the near term, the outlook is murkier. The Trump administration is right to start looking beyond old arms-control frameworks of diminishing strategic value to the US Moving from those frameworks to something better will be the big challenge for Trump and, one suspects, his successors. Bloomberg