The Russian military has reportedly deployed a new, nuclear-armed cruise missile, in direct violation of a 1987 treaty with the United States that bans hard-to-defeat medium-range, land-based nukes.

The deployment of the truck-launched SSC-8 missile apparently somewhere in Eastern Europe, first reported by The New York Times, could escalate nuclear competition between the United States and Russia.

President Trump and his allies in the U.S. Congress have, in just the first few weeks of Trump's administration, already threatened to dismantle hard-won, Cold War-era arms-control measures—the same kinds of measures Russia is now defying. Increasingly unconstrained by treaties, the United States and Russia are set to grow and improve their atomic arsenals, which could greatly raise the risk of nuclear war.

“I think we are in a new arms race,” Tom Collina, policy director at San Francisco-based Ploughshares, an anti-nuclear advocacy group, told The Daily Beast. "The U.S. plans to spend $1 trillion over the next 30 years on nuclear weapons, including new ones. Russia is rebuilding its forces. The rhetoric is getting heated and threatening."

U.S. intelligence detected the SSC-8’s development sometime before 2014. That year, the Obama administration began vaguely referring to a new Russian weapon that, the administration claimed, violated the 1987 Intermediate-Range Nuclear Forces treaty.

The INF agreement, signed by U.S. President Ronald Reagan and Soviet leader Mikhail Gorbachev, banned nuclear and non-nuclear ground-launched missiles with ranges between 620 and 3,420 miles. By 1991, the United States and Russia together had decommissioned around 2,700 existing missiles that the new treaty prohibited.

The 1987 deal helped to eliminate some of the most destabilizing types of nuclear weapons. Intermediate-range weapons can strike quickly, compelling rival atomic powers to keep their own forces on high alert. And unlike ICBMs, the shorter-range nukes are indistinguishable from non-nuclear short-range missiles at the time of launch, increasing the chance that a country might mistake a conventional military operation for an atomic sneak attack.

The regime of Russian President Vladimir Putin is not fond of the INF treaty. From Moscow’s point of view, the treaty preserves America’s existing advantages in sea-launched cruise missiles and anti-ICBM defenses while making it more difficult for Russia to develop weapons that exploit gaps in American technology and strategy. “The narrative in Moscow is that they got a bad deal,” Collina said.

Experts agree that the acceleration of U.S. missile-defense tech under Presidents George W. Bush and Barack Obama, all in the context of an expanding NATO, provoked Russia’s development of the SSC-8. The final provocation was apparently the Pentagon’s installation of SM-3 ballistic-missile interceptors in Romania in 2015. The U.S. military is building a similar missile-defense site in Poland.

The Pentagon intends the SM-3 sites to help protect America’s NATO allies in Europe from Iranian rockets, but the Kremlin considers them a threat to the strategic balance of power between the United States and Russia. “Large-scale deployment [of missile-defenses] could deprive Moscow of that ultimate security guarantee” that nukes provide, Nikolai Sokov, a fellow at the Middlebury Institute of International Studies at Monterey, told The Daily Beast.

Feeling threatened, Russia has threatened back. And the timing could not be worse for peace advocates. Where the Obama administration defended existing nuclear treaties and worked to slowly reduce America’s and Russia’s nuclear arsenals, the Trump administration seems determined to tear up decades worth of arms-controls measures.

Trump has urged Japan and South Korea to field their own nukes and has threatened to scrap the international deal with Iran that limits that country’s nuclear-weapons program. In a phone call with Putin on Feb. 9, Trump trash-talked New START, the 2011 treaty that limits the United States and Russia to 1,500 deployed nuclear warheads apiece.

Confusingly, Trump has also said that “nuclear weapons should be way down and reduced very substantially.”

Meanwhile, two of Trump’s close congressional allies—Arkansas Sen. Tom Cotton and South Carolina Rep. Joe Wilson—have proposed to defund the international organization that monitors and helps to prevent nuclear-weapons tests.

New Russian nuke deployments “can’t go unanswered,” U.S. Air Force Gen. Philip Breedlove, who was NATO’s top officer before he retired in 2016, told The New York Times. But with more and more nuclear-disarmament efforts collapsing, America must be careful not to answer Russia’s new nukes with new nukes of its own.

“We make new deployments that threaten Russia while sincerely negotiating a return to compliance,” Jeffrey Lewis, also with the Middlebury Institute of International Studies at Monterey, told The Daily Beast.

“I’d make the new deployments conventional-only”—that is, non-nuclear—“and, if possible, INF-compliant,” Lewis said, adding that the Trump administration should also bolster U.S. forces within the context of NATO.

“We need to show the Russians that NATO is capable of responding in a unified fashion. They are hoping to break NATO. Our goal is to make it clear that Russia’s behavior is why NATO is still necessary.”

But worryingly, Trump has repeatedly attacked NATO as outdated and a drain on America’s finances. “I said a long time ago that NATO had problems,” Trump said in January. “No. 1, it was obsolete, because it was, you know, designed many, many years ago. No. 2, the countries aren’t paying what they’re supposed to pay."

A stronger NATO could be the United States' best response to Russia's nuclear escalation. But a weaker NATO is the likely result of Trump's attacks on the alliance. On its own against a rearming Russia, the United States risks embracing the apocalyptic thinking of the early Cold War. "It is time for both sides to step back from the brink and rethink what they are doing," Collina said. "They are in a race in which they can only lose."