President Joe Biden said he does not believe that Russian President Vladimir Putin would use a tactical nuclear weapon on Ukraine.

“I think it’s irresponsible for him to talk about it, the idea that a world leader of one of the largest nuclear powers in the world says he may use a tactical nuclear weapon in Ukraine,” Biden told CNN’s Jake Tapper in an exclusive interview with the network.

“The whole point I was making was it could lead to just a horrible outcome. And not because anybody intends to turn it into a world war or anything, but just once you use a nuclear weapon, the mistakes that can be made, the miscalculations, who knows what would happen,” Biden continued.

When asked if the United States had considered what would happen if Putin did use a nuclear weapon and what the “red line” for his administration would be, Biden said it would be irresponsible of him to discuss specifics but made it clear that the Pentagon did not have to be asked to game out potential outcomes.