The US military’s top spokesperson tamped down concerns of an imminent nuclear threat from Russia, days after Joe Biden warned of a potential nuclear “armageddon”.

Speaking at a Democratic fundraiser this week, Biden talked bluntly about the threat of a nuclear attack from Russia. “We have not faced the prospect of armageddon since Kennedy and the Cuban missile crisis,” the president said. He added that Russian leader Vladimir Putin was “not joking when he talks about potential use of tactical nuclear weapons or biological or chemical weapons because his military is, you might say, significantly underperforming” after invading Ukraine earlier this year.

Echoing comments from the White House earlier this week, top Pentagon spokesperson John Kirby said Biden’s comments were not based on specific new information.

“His comments were not based on new or fresh intelligence or new indications that Mr Putin has made a decision to use nuclear weapons,” Kirby told Martha Raddatz in an interview on ABC News’ This Week. “Quite frankly, we don’t have any information that he has made that kind of decision. Nor have we seen anything that would give us pause to reconsider our own strategic nuclear posture.”

Biden’s remarks invoking Armageddon drew a sharp rebuke from former secretary of state Mike Pompeo, a member of the Donald Trump White House’s cabinet who is mulling a 2024 presidential run.

“Those comments were reckless” and “a terrible risk to the American people”, Pompeo said on the Republican-friendly Fox News network.

Kirby on Sunday also declined to weigh on a recent explosion on the Kerch Bridge linking Russia and Crimea, the Ukrainian territory under Russian control.

The explosion dealt a blow to Russian military logistics and embarrassed Putin, for whom the bridge had symbolic personal importance. Ukraine has not yet claimed responsibility for the attack, but it has been celebrated by senior leaders in the country.

“We don’t really have anything more to add to the reports about the explosion on the bridge,” Kirby said. “I just don’t have anything more to contribute to that this morning.”

Kirby also addressed Biden’s comments last week that the US was trying to find where Putin could get an “off ramp” to the war on Ukraine.

“Mr Putin started this war and Mr Putin could end it today, simply by moving his troops out of the country,” Kirby said. “He’s the one who chose to start this conflict again and he can choose to end it.”

Russian forces invaded Ukraine in February. But Ukraine’s defenders in recent weeks have taken back some of the territories it had lost control of during the invasion.

With its hold on Ukraine weakening, Putin recently ordered the mobilization of reservists to reinforce the invasion, which ignited protests in dozens of cities across Russia and has led to long lines at its land borders with other countries.