THIRTY years ago, Ronald Reagan and Mikhail Gorbachev signed the Intermediate-Range Nuclear Forces (INF) treaty, banishing an entire category of destabilising weapons from Europe. Some 2,700 ground-launched ballistic and cruise missiles with ranges between 500 and 5,500 km were destroyed in a deal that presaged the end of the cold war. Yet today the treaty is imperiled by Russian violations. If those do not cause it to collapse, the response America is contemplating may.

America first announced its concerns over Russian violations in 2014, a few months after Vladimir Putin annexed Crimea. The treaty obliges both countries not to possess, “produce or flight-test” new intermediate-range ground-launched missiles. Russia, the Americans said, had tested a cruise missile that breached that agreement. No countermeasures were proposed, apparently in the hope that the Russians would be embarrassed into quietly abandoning the new system.

The Russians denied the charge, though they had been complaining about the treaty for years, saying it blocked them from deterring new missile powers. (China, India, Pakistan, North Korea and Israel, they noted, all have intermediate-range missiles.) Another reason why America hesitated to retaliate was that it was focused on deploying new troops to NATO’s eastern members, who were worried by Russia’s intervention in Ukraine. The threat to the treaty was seen as a slow-burn problem that could be addressed later.

That time appears to have come. In February Donald Trump’s administration revealed that Russia had secretly begun deploying the new missile, known as the SSC-8, a ground-launched variant of the 3M14 naval cruise missile used on targets in Syria two years ago. The SSC-8 can be moved by road and has a range of 2,500 km. The Russians have two operational battalions, each with about 36 missiles. One is thought still to be at the Kapustin Yar test site near Volgograd, the other at a base in the central military district that puts it in range of targets across Europe.

The Trump administration is expected to publish its Nuclear Posture Review early next year, which will guide its nuclear weapons policy. Officials are seeking ways to bring Russia back into compliance with the treaty rather than walking away from it. But some in the administration are sceptical about all arms-control agreements, and the INF treaty in particular. Last month Congress authorised the Pentagon to spend $58m on a response. The plan includes initial development of a new American intermediate-range missile. That would not breach the treaty, but most arms-control experts regard it as a step in the wrong direction. Producing such a missile would take many years and cost billions of dollars that the Pentagon can ill afford. The effort to persuade European members of NATO to host the missiles would divide the alliance, and the Russians could claim that not they, but the Americans, had blown up the treaty.

Steven Pifer, a former arms-control negotiator at the Brookings Institution, a think-tank, says that it makes no sense to give Mr Putin exactly what he wants. He reckons there are better ways to put pressure on Russia. One would be deploying existing air- and sea-launched cruise missiles to Europe and nearby waters. B-1 strategic bombers armed with stand-off missiles could be stationed at Fairford, an American base in Britain. Submarines carrying cruise missiles might turn up on patrol in the North Sea. Mr Pifer also thinks it is high time that America’s European allies, in particular France and Germany, criticised the Kremlin’s behaviour, which is a threat not just to the treaty but to them.

It may be too late to save the INF treaty, but it is worth an effort. If the treaty dies, the prospects for extending the New START strategic weapons deal, which will otherwise expire in 2021, will be dim. So will the future of nuclear-arms control itself.