President Biden offered a curt response when asked Monday whether Americans should be worried about the possibility of nuclear war breaking out with Russia: "No."

Biden was attending a White House celebration of Black History Month when he was asked by CBS News reporter Nancy Cordes about about the threat, given Russian President Vladimir Putin's announcement the day before that he had placed his country's nuclear forces on a state of "special combat readiness."

On Sunday, U.S. Ambassador to the United Nations Linda Thomas-Greenfield called out Putin's alert.

"President Putin is continuing to escalate this war in a manner that is totally unacceptable, and we have to continue to condemn his actions in the strongest possible way," she said in an interview on CBS' "Face the Nation." "Our voices have been unified with the Europeans and with the world that he needs to cease his aggressive actions toward Ukraine."

At the same time, Thomas-Greenfield also noted that Russia was “under no threat” from the U.S. military.

Also on Sunday, White House Press Secretary Jen Psaki sought to downplay Putin's comment on Russia's nuclear forces.

"This is really a pattern that we've seen from President Putin through the course of this conflict, which is manufacturing threats that don't exist in order to justify further aggression — and the global community and the American people should look at it through that prism," Psaki said in an interview on ABC's "This Week."

U.S. officials said Monday that despite Putin's move, there was no need to change the country's nuclear alert level.

Those assurances aside, the U.S. and its NATO allies find themselves in a tricky situation — supplying money and weapons to Ukraine's outnumbered military forces, while stopping short of offering to intervene directly. While some Republican lawmakers have urged President Biden to consider implementing a no-fly zone over Ukraine, the administration has ruled that out. “It would essentially mean the U.S. military would be shooting down planes, Russian planes," Psaki said in a Monday interview on MSNBC. "That is definitely escalatory. ... That is not something the president wants to do."

The U.S. and Russia possess the two largest nuclear arsenals on Earth, with more than enough missiles and bombs to wipe out humankind.

Speaking at the United Nations on Monday, Ukrainian Ambassador Sergiy Kyslytsya referenced Putin's nuclear decision with an allusion to Adolf Hitler.

“If [Putin] wants to kill himself, he doesn’t need to use a nuclear arsenal. He has to do what the guy in Berlin did in a bunker in May 1945," Kyslytsya said, in reference to the Nazi dictator's suicide at the end of World War II.