The US plans to test missiles banned for decades. Some fear it could spark an arms race.

The United States plans to test missiles, banned for decades, that could greatly increase tensions with Russia and conceivably kick off an arms race.

Unnamed senior defense officials told reporters on Wednesday that the Trump administration wants to try out two different weapons. The first, to be tested in August, is a ground-launch cruise missile that can fly just over 600 miles. And the second, planned for testing in November, is a ballistic missile that can travel between 1,865 and 2,485 miles.

It’s worth noting that these are conventional weapons — which means they’re not nuclear — but they could potentially be armed with nuclear warheads in the future.

These tests might seem ordinary; after all, militaries try out new weaponry all the time. But they actually symbolize the complete break from a Cold War-era agreement between Washington and Moscow.

The Intermediate-Range Nuclear Forces Treaty was signed by President Ronald Reagan and Soviet leader Mikhail Gorbachev in December 1987. The agreement prohibited Washington and Moscow from fielding ground-launched cruise missiles that could fly between 310 and 3,420 miles. But President Donald Trump announced in February that the US was leaving the deal, citing repeated Russian violations of the accord (which Moscow denies).

Unless Russia comes back into compliance with the agreement, which is highly unlikely, America will officially withdraw in August. Mere days later, the US military will test the ground-launched missile.

It’s still early in the process, though. For one, these are simply tests, which means the Trump administration has yet to actually mass-produce the weapons. And it’s unclear if American allies in Europe and Asia would allow the US to base the missiles in their countries, as that could potentially provoke Russia and China.

“We haven’t engaged any of our allies about forward deployment,” a defense official told reporters this week. “Honestly, we haven’t been thinking about this because we have been scrupulously abiding by the treaty.”

The problem is that the tests mean we’re entering a new world: one in which constraints on how powerful nations can threaten each other are going away.

So will these tests fuel an arms race? Or will they merely help make the US stronger at defending against China and Russia? Analysts who track these kinds of things are widely split.

Some fear that simply conducting these tests could further heighten competition among Washington, Moscow, and Beijing.

“This is how arms races usually start,” Grace Liu, a missile expert at the Middlebury Institute of International Studies, told me. “It starts when one side thinks it’s not being tough enough and decides to escalate in some way.”

“Introducing new capabilities and doing something that was previously prohibited is probably the most aggressive way to go,” she added.

Others, like missile expert Thomas Karako of the Center for Strategic and International Studies in Washington, say there are valid reasons for trying out previously banned missiles.

Adding these new weapons to America’s already formidable arsenal could make it harder for adversaries to track and defend against a US attack, he said. The key, really, is dispersing the missiles throughout a large land area so they’re not as vulnerable to a Chinese or Russian strike. “We want China and Russia to wake up every single day and think that today is not a good day to test the resolve of the United States,” Karako told me.

Every expert I spoke to warned that it’s too early to draw concrete conclusions: The US hasn’t even officially left the treaty with Russia, and the Pentagon is only in the testing phase with the weapons.

But the fact that the US is openly considering testing these once-banned weapons shows that the decades-long understanding between the US and Russia over missiles is crumbling — and it’s unclear what comes next.