Russian President Vladimir Putin suspended Moscow's participation in the last remaining nuclear arms control pact with the United States, announcing the move Tuesday in a bitter speech where he made clear he would not change his strategy in the war in Ukraine.

In his long-delayed state-of-the-nation address, Putin cast his country — and Ukraine — as victims of Western double-dealing and said it was Russia, not Ukraine, fighting for its very existence.

"We aren't fighting the Ukrainian people," Putin said ahead of the war's first anniversary Friday. "The Ukrainian people have become hostages of the Kyiv regime and its Western masters, which have effectively occupied the country."

The speech reiterated a litany of grievances he has frequently offered as justification for the widely condemned military campaign while vowing no military letup in a conflict that has reawakened Cold War fears.

On top of that, Putin sharply upped the ante by declaring Moscow would suspend its participation in the New START Treaty. The pact, signed in 2010 by the U.S. and Russia, caps the number of long-range nuclear warheads the two sides can deploy and limits the use of missiles that can carry atomic weapons.

Putin also said Russia should stand ready to resume nuclear weapons tests if the U.S. does so, a move that would end a global ban on such tests in place since the Cold War era.

U.S. Secretary of State Antony Blinken described Moscow's decision as "really unfortunate and very irresponsible."

"We'll be watching carefully to see what Russia actually does," he said while visiting Greece.

It was the second time in recent days the Ukraine war showed it could spread into perilous new terrain, after Blinken told China at the weekend that it would be a "serious problem" if Beijing provided arms and ammunition to Russia.

China and Russia have aligned their foreign policies to oppose Washington. Beijing has refused to condemn Russia's invasion or atrocities against civilians in Ukraine while strongly criticizing Western economic sanctions on Moscow. At the end of last year, Russia and China held joint naval drills in the East China Sea.

The deputy head of Ukraine's intelligence service, Vadym Skibitskyi, told The Associated Press that his agency hasn't so far seen any signs that China is providing weapons to Moscow.

Russia invaded Ukraine on Feb. 24, 2022, and made a dash toward Kyiv, apparently expecting to overrun the capital quickly. But stiff resistance from Ukrainian forces — supported by Western weapons — turned back Moscow's troops. While Ukraine has reclaimed many areas initially seized by Russia, the sides have become bogged down elsewhere.

The war has revived the divide between Russia and the West, reinvigorated the NATO alliance, and created the biggest threat to Putin's rule of more than two-decades. U.S. President Joe Biden, fresh off a surprise visit to Kyiv, was in Poland on Tuesday to solidify that Western unity.

While Russia's Constitution mandates that the president deliver the speech annually, Putin never gave one in 2022, as his troops rolled into Ukraine and suffered repeated setbacks. Much of it covered old ground, as Putin offered his own version of recent history, discounting Ukraine's arguments that it needed Western help to thwart a Russian military takeover.

"Western elites aren't trying to conceal their goals, to inflict a 'strategic defeat' to Russia," Putin said in the speech broadcast on all state TV channels. "They intend to transform the local conflict into a global confrontation."

He added that Russia was prepared to respond since "it will be a matter of our country's existence." He has repeatedly depicted NATO's expansion to include countries close to Russia as an existential threat to his country.

Italian Premier Giorgia Meloni, who was in Ukraine on Tuesday, said she hoped Putin had taken a different approach.

"What we heard this morning was propaganda that we already know," Meloni said in English. "He says (Russia) worked on diplomacy to avoid the conflict, but the truth is that there is somebody who is the invader and somebody who is defending itself."

Putin denied any wrongdoing in Ukraine, even after Kremlin forces struck civilian targets, including hospitals, and are widely accused of war crimes. Ukraine's military reported Tuesday that Russian forces shelled the southern cities of Kherson and Ochakiv while Putin spoke, killing six.

President Volodymyr Zelenskyy lamented that Russian forces were "again mercilessly killing the civilian population."

Putin began his speech with strong words for those countries that provided Kyiv with crucial military support and warned them against supplying any longer-range weapons.

"It's they who have started the war. And we are using force to end it," Putin said before an audience of lawmakers, state officials and soldiers.

Putin also accused the West of taking aim at Russian culture, religion and values because it is aware that "it is impossible to defeat Russia on the battlefield."

Likewise, he said Western sanctions hadn't "achieved anything and will not achieve anything."

Reflecting the Kremlin's clampdown on free speech and press, it barred coverage of the address by media from "unfriendly" countries, including the U.S., the U.K. and those in the European Union, with Kremlin spokesman Dmitry Peskov saying their journalists could watch the broadcast.

He previously told reporters that the speech's delay had to do with Putin's "work schedule," but Russian media reports linked it to the setbacks by Russian forces. The Russian president also postponed the state-of-the-nation address in 2017. Last year, the Kremlin also canceled two other big annual events — Putin's news conference and a highly scripted phone-in marathon taking questions from the public.

Analysts expected Putin's speech would be tough in the wake of Biden's visit to Kyiv on Monday, which he did not mention. In his his own speech later Tuesday, Biden is expected to highlight the commitment of the central European country and other allies to Ukraine over the past year.

White House national security adviser Jake Sullivan said that Biden's address would not be "some kind of head to head" with Putin's.

"This is not a rhetorical contest with anyone else," said.