After weeks of threats from Moscow and fears of escalation in the conflict, the Russian leader had earlier in the day played down the idea of the Kremlin taking such a drastic step.
But Biden expressed skepticism and criticized Putin for what he called "dangerous" brinkmanship.
“I think if he has no intention, why does he keep talking about it? Why does he talk about the ability to use a tactical nuclear weapon?" Biden told NewsNation in an interview late Thursday in Syracuse, New York.
"He’s been very dangerous with how he’s approached this, and he should just get out — he could end this all, get out of Ukraine,” Biden added.
The president was responding to comments made by the Russian leader in a typically grandiose speech Thursday that lasted more than three hours and covered topics ranging from culture wars to the Kremlin's invasion of its neighbor.
“We do not need a nuclear strike on Ukraine, there is no point — neither political nor military,” Putin said in the speech.
He instead sought to blame the United States and its allies, insisting Russia had only been responding to Western nuclear "blackmail."
The Kremlin has stoked growing nuclear fears as its military retreats on the battlefield and disquiet grows at home, with Russian officials repeatedly suggesting that it would be willing to use nuclear weapons to protect annexed territory where Ukrainian forces are making gains.
In an address to the nation last month, Putin said that if Russia’s “territorial integrity” was threatened, “we will certainly use all the means at our disposal” to retaliate — and added that “it’s not a bluff.”
Washington has made clear it has warned Russia there will be “catastrophic” consequences if it uses nuclear weapons, but U.S. officials and experts have downplayed any imminent threat.
There was nothing new in Putin’s latest statements regarding nuclear weapons and how Russia intends to use them, said Andrey Baklitskiy, a senior researcher at the Geneva-based United Nations Institute for Disarmament Research.
“What he means when he talks about nuclear weapons is nuclear deterrence against NATO and the United States, either attacking Russia with nuclear weapons or attacking Russia directly, which can escalate to the nuclear level,” Baklitskiy said Friday by telephone.
Putin observed exercises by Russia’s strategic nuclear forces Wednesday, with two U.S. officials saying that Moscow had informed the U.S. about the annual drills, as it is obliged to do under the New START nuclear treaty. The officials said the U.S. has no indications Russia is preparing to use a nuclear weapon inside Ukraine but continues to watch the situation closely.
Defense Secretary Lloyd Austin said in a Pentagon briefing Thursday that the U.S. has not seen anything to indicate Russia is using the exercise as a cover to launch a nuclear strike. He added that the U.S. is concerned about the conflict in Ukraine escalating but said there are still no indications Russia is planning to use a nuclear weapon.
In recent days the focus of international concern has been on Russian claims that Ukraine could detonate a "dirty bomb" to frame Moscow — an allegation dismissed by Kyiv and the West as baseless and a potential "false-flag" operation or effort to build a pretext for Russian escalation.
Putin repeated the accusation in his speech Thursday.
“Kyiv is seeking some kind of nuclear incident to inflate a new round of struggle against Russia,” he said.
“It’s not for nothing that we said about the “dirty bomb” that Kyiv is creating, we even know where it is being made," the Russian leader said. "I instructed Shoigu to call foreign colleagues and warn them about the threat of this provocation," he added, referring to the sudden flurry of calls from his defense minister that sparked alarm in Western capitals.
A dirty bomb, also known as a “radiological dispersion device,” is a conventional weapon that has been augmented with a radioactive material. Traditionally, security experts have warned of dirty bombs being used by terrorist groups, instead of militaries.
Asked about the Russian claims earlier this week, Biden said he had "spent a lot of time" talking about the subject Tuesday.
"Let me just say: Russia would be making an incredibly serious mistake for it to use a tactical nuclear weapon," he added. "I’m not guaranteeing you that it’s a false-flag operation yet; I don’t know. But it would be a serious, serious mistake."