Russian President Vladimir Putin is healthy, sane and "in better shape than ever", his close ally Belarus President Alexander Lukashenko has said in an interview with the Japanese television channel TBS.
"He and I haven't only met as heads of state, we're on friendly terms," Mr Lukashenko said in a recording of the interview shared by state news agency BelTA. "I'm absolutely privy to all his details, as far as possible, both state and personal."
Russia used Belarusian territory as a staging post for its invasion of Ukraine on Feb 24.
Western leaders have suggested Mr Putin made a costly miscalculation by launching the military assault on Ukraine, where Russian forces have taken heavy losses and their advance has largely stalled despite their apparent superiority.
British Prime Minister Boris Johnson has suggested Mr Putin is being "irrational" and Dutch Prime Minister Mark Rutte has described him as "totally paranoid".
But Mr Lukashenko dismissed the notion that Mr Putin, who is 69, was not at the height of his powers.
"The West, and you, should get this stupidity, this fiction out of your heads," he told the interviewer.
"Putin is absolutely fit, he's in better shape than ever... This is a completely sane, healthy person, physically healthy, he's an athlete. As they say here - he'll catch a cold at all our funerals."
Mr Lukashenko, 67, also bemoaned the break-up of the Soviet Union in 1991. The theme is one Mr Putin has frequently discussed, not least when he suggested in speeches before the invasion that Ukraine was an artificial construct and an "inalienable part" of Russian history and culture.
"The collapse of the Soviet Union is a tragedy," Mr Lukashenko said. "If the Soviet Union had survived to this day, we could have avoided all sorts of conflicts in the world...
"While the USSR existed, the world was multipolar and one pole balanced the other," he said. "Now the reason for what's happening in the world is unipolarity - the monopolisation of our planet by the United States of America."