In an interview with state media, Putin, who launched a full-scale invasion of Ukraine and is nearly certain to win the March 15 to 17 presidential election, said Russia would be ready to use nuclear weapons if its sovereignty was threatened.
"From a military-technical point of view, we are, of course, ready," Putin told Rossiya-1 television and news agency RIA in response to a question whether the country was really ready for a nuclear war.
He said the United States understands that if it deploys American troops on Russian territory - or to Ukraine - Russia would treat the move as an intervention.
"(In the United States) there are enough specialists in the field of Russian-American relations and in the field of strategic restraint," Putin said.
"Therefore, I don’t think that here everything is rushing to it (nuclear confrontation), but we are ready for this."
He reiterated that the use of nuclear weapons was spelled out in the Kremlin's nuclear doctrine, its policy setting out the circumstances in which Russia might use its weapons.
"Weapons exist in order to use them," Putin said. "We have our own principles."
If the United States conducted nuclear tests, Russia might do the same, he added in the wide-ranging interview.
"It's not necessary ... we still need to think about it, but I don't rule out that we can do the same."
However, Putin said Russia had never faced a need to use nuclear weapons in Ukraine, where the conflict has raged since February 2022.
"Why do we need to use weapons of mass destruction? There has never been such a need."
