Putin Lowers Nuclear Weapons Threshold After U.S. Allows Ukraine to Use Missiles Against Russia

President Vladimir V. Putin on Tuesday lowered Russia’s threshold for the use of nuclear weapons, a long-planned move whose timing appeared designed to show the Kremlin could respond aggressively to Ukrainian strikes on Russian territory with American missiles.

The decree signed by Mr. Putin implemented a revised version of Russia’s nuclear doctrine that Mr. Putin described in televised remarks in September. But the timing sent a message, coming just two days after the news that President Biden had authorized the use of U.S.-supplied longer-range missiles by Ukraine for strikes inside Russia.

Asked whether Russia could respond with nuclear weapons to such strikes, Dmitri S. Peskov, Mr. Putin’s spokesman, repeated the new doctrine’s language that Russia “reserves the right” to use such weapons to respond to a conventional-weapons attack that creates a “critical threat” to its “sovereignty and territorial integrity.”

Russia’s Ministry of Defense later announced that Kyiv had used the ballistic missiles known as the Army Tactical Missile System, or ATACMS, in a pre-dawn attack on an ammunition depot in southwestern Russia. A senior American and a senior Ukrainian official, both of whom spoke on the condition of anonymity to discuss ongoing operations, confirmed that the strikes used ATACMS, which have a range of 190 miles, the longest of any munitions the West has given to Ukraine.

The White House played down Mr. Putin’s new doctrine. In a statement issued by the National Security Council, the White House noted that it had observed “no changes to Russia’s nuclear posture.”

The new doctrine, published Tuesday on the Kremlin website, differs from the previous iteration in at least two important ways that show how Mr. Putin is trying to use the threat of his nuclear arsenal to deter the United States from further supporting Ukraine.

First, it raises the possibility that nuclear weapons could be used against a nuclear-armed country that doesn’t directly launch an attack on Russia but supports one by a nonnuclear country. That is a clear reference to Ukraine and its nuclear-armed backers, led by the United States. Russia’s previous nuclear doctrine focused on responding to attacks by nuclear-armed countries and alliances.

Second, it lowers the threshold at which Russia could consider nuclear use in response to an attack with conventional weapons. The previous doctrine, published in 2020, said such an attack must threaten “the very existence of the state,” while the new one puts that threshold at a “critical threat” to Russia’s sovereignty.

The doctrine’s publication on Tuesday appeared to be the latest suggestion from the Kremlin that Russia could use nuclear weapons to respond to attacks by Ukraine carried out with American support, and that the response could be directed against American facilities as well as Ukraine itself.

“Aggression against the Russian Federation and (or) its allies by any nonnuclear state with the participation or support of a nuclear state is considered as their joint attack,” the document says.

Mr. Peskov, speaking at his daily conference call with reporters, pointed to this section of the revised doctrine, saying, “this is also a very important paragraph.”

“Nuclear deterrence is aimed at ensuring that a potential adversary understands the inevitability of retaliation in the event of aggression against the Russian Federation and/or its allies,” Mr. Peskov said.

In the statement from the National Security Council, the White House noted that it was “not surprised” by the new decree since Mr. Putin had signaled the change months ago.

“This is more of the same irresponsible rhetoric from Russia, which we have seen for the past two years,” the statement said. The White House made no linkage between its lifting of restrictions on Ukraine and Mr. Putin’s announcement.

Western officials have previously said that they would be most worried about Moscow’s using nuclear weapons if the Russian military is on its back foot, and for the moment the war in Ukraine largely appears to be going Mr. Putin’s way.

On the battlefield, Russian forces are advancing in eastern Ukraine, while Kyiv struggles with recruitment and morale. And in geopolitics, Mr. Putin has also been making gains: his phone call last week with Chancellor Olaf Scholz of Germany broke two years of diplomatic isolation by the biggest Western countries, while the election of Donald J. Trump as incoming president of the United States has raised hopes in Russia of a Ukraine peace deal on the Kremlin’s terms.

From the first day of his invasion of Ukraine in February 2022, Mr. Putin has been trying to use the threat of Russia’s enormous nuclear arsenal to deter Western military aid to Ukraine. He has had only limited success, with the United States leading a coalition that has dispatched tens of billions of dollars’ worth of modern tanks, artillery systems and missiles.

But Mr. Putin has sought to draw a new red line at Ukraine’s using Western missiles to attack deep inside Russian territory. To the frustration of Ukrainian officials, President Biden had long refused to allow the weapons to be used that way, given what American officials said was the risk of a violent response by Mr. Putin and the limited impact that the use of those missiles could have on the battlefield.

But Mr. Biden changed course recently after Russia’s surprise decision to bring North Korean troops into the fight, American officials said.

In September, Mr. Putin warned that if the United States and its allies permitted Ukraine to fire missiles deeper into Russia, they would put his country “at war” with NATO. Ukraine has used homegrown weapons to attack at longer ranges.

In the lead-up to Mr. Biden’s decision, some American officials said they feared that Ukraine’s use of the missiles across the border could prompt Mr. Putin to retaliate with force against the United States and its coalition partners. Other American officials said they thought those fears were overblown.

In response to Mr. Biden’s recent decision, Russian officials have warned in some of their strongest statements yet about the risk of nuclear war. On Tuesday, Andrei Kartapolov, the head of the defense committee in Russia’s lower house of Parliament, said that Mr. Biden “will slam the lid of his own coffin and drag many, many more people with him.”

The question now is whether Mr. Putin sees a strategic advantage to intensifying his conflict with the United States — even by nonnuclear means — given Mr. Trump’s imminent return to the White House.

Tatiana Stanovaya, a senior fellow at the Carnegie Russia Eurasia Center, described the situation on X as an “extraordinarily dangerous juncture” because Mr. Putin might see the temptation to escalate the war before Mr. Trump takes office in order to force a peace deal on his terms.

But some analysts still predicted that given Mr. Trump’s stated goal of ending the war quickly, Mr. Putin’s more rational course would be to avoid any actions that would further escalate his conflict with the United States.

A Moscow-based analyst whose organization is close to the Russian government said that while Ukraine’s ATACMS strikes were unlikely to change the course of the war, an aggressive response against the United States “will create problems for Trump.”

“It’ll be harder for him to turn the situation around if that’s what he wants to do,” the analyst said, speaking on the condition of anonymity because he wasn’t authorized to comment to Western media.

Oleg Matsnev and David E. Sanger contributed reporting.