Kyiv/Moscow - Russian President Vladimir Putin in a defiant speech on Tuesday delivered a nuclear warning to the West over Ukraine, suspending a landmark nuclear arms control treaty, announcing new strategic systems had been put on combat duty and warning that Moscow could resume nuclear tests.

Speaking nearly a year to the day since ordering an invasion that has triggered the biggest confrontation with the West since the 1962 Cuban Missile crisis, Putin said Russia would achieve its war aims and accused the West of trying to destroy Russia.

"The elites of the West do not hide their purpose. But they also cannot fail to realise that it is impossible to defeat Russia on the battlefield," a defiant Putin told his country's political and military elite.

Cautioning the United States that it was stoking the war into a global conflict, Putin said that Russia was suspending participation in the New START Treaty, the last major arms control treaty between Moscow and Washington. The treaty caps the number of deployed strategic nuclear warheads that the United States and Russia can deploy and was due to expire in 2026.

"I am forced to announce today that Russia is suspending its participation in the Strategic Arms Reduction Treaty," said Putin.

The Russian leader said, without citing evidence, that some people in Washington were thinking about resuming nuclear testing. Russia's defence ministry and nuclear corporation should therefore be ready to test Russian nuclear weapons if necessary, he said.

"Of course, we will not do this first. But if the United States conducts tests, then we will. No one should have dangerous illusions that global strategic parity can be destroyed," Putin said.

"A week ago, I signed a decree on putting new ground-based strategic systems on combat duty. Are they going to stick their nose in there too, or what?"

It was not immediately clear which ground-based systems had been put on combat duty. Putin said Ukraine had sought to strike a facility deep inside Russia where some of its nuclear bombers are based, a reference to the Engels air base.

The Ukraine conflict is by far the biggest bet by a Kremlin chief since at least the 1991 fall of the Soviet Union - and a gamble Western leaders such as U.S. President Joe Biden, who visited Kyiv on Monday, say he must lose.

Russian forces have suffered three major battlefield reversals since the war began but still control around one fifth of Ukraine. Tens of thousands of men have been killed on both sides.

Speaking for one hour and 45 minutes below a large emblem bearing the two-headed eagle of Russia, and flanked by a total of eight tricolour Russian flags, Putin vowed to continue until he achieved his aims in Ukraine.

Putin accused the U.S.-led NATO alliance of fanning the flames of the conflict in the mistaken belief that it could defeat Moscow in a global confrontation.

"They intend to transform a local conflict into a phase of global confrontation. This is exactly how we understand it all and we will react accordingly, because in this case we are talking about the existence of our country," Putin said.

The United States says it is concerned Beijing may be considering supplying weapons to Russia, a step that would risk a potential escalation of the Ukraine war into a confrontation between Russia and China on the one side and Ukraine and the U.S.-led NATO military alliance on the other.

Besides the promise to continue the war and warnings to the West of a global confrontation, Putin also sought to justify the war, saying it had been forced on Russia and that he understood the pain of the families of those who had fallen in battle.

The West and Ukraine reject that narrative, and say NATO expansion eastwards since the Cold War ended is no justification for what they say is an imperial-style land grab doomed to failure.

"The people of Ukraine have become the hostage of the Kyiv regime and its Western overlords, who have effectively occupied this country in the political, military and economic sense," Putin said.

"They intend to transform a local conflict into a phase of global confrontation. This is exactly how we understand it all and we will react accordingly, because in this case we are talking about the existence of our country."

Russia would never yield to Western attempts to divide its society, said the 70-year-old Kremlin chief, adding that a majority of Russians support the war.