"It's hard for me to comment on what the US president has been saying lately, as it is for other observers in general who are wondering how to interpret it all. I wouldn't put too much weight on verbal escapades that have no basis in fact right now," the top Russian diplomat said in an interview with the "Moscow.Kremlin. Putin" TV program, according to an excerpt posted on Sunday on journalist Pavel Zarubin's Telegram channel, TASS reported.
Lavrov called Zelensky's statements "even more turbulent stream of consciousness."
"I have no medical background. (Head of the European Commission) Ursula von der Leyen has a medical degree. I cannot be responsible for the psychological state of people who repeatedly, daily prove their inadequacy," Lavrov added.
Earlier, Biden said during a speech in California that he believed the threat of Russian leader Vladimir Putin using tactical nuclear weapons was real.