Biden calls Zelenskyy 'Putin', Kamala Harris 'Vice President Trump' | Watch

Amid concerns of his fitness to run for a second term, US President Joe Biden made twin gaffes, first while addressing a NATO event and later at a presser in Washington.

In the first instance, Biden introduces Ukraine President as Putin.

Hours later at a press conference, Biden called Kamala Harris 'Vice President Trump'.

Biden defended calling Zelensky Putin, asserting that the conference was successful.

"Did you see any damage to our stand in my leading this conference? Have you seen a more successful conference? What do you think? And the Putin piece, I was talking about Putin and I said, 'and now at the very end, I said here, I mean Putin. I said, no, I'm sorry, Zelenskyy'," said Biden.

"It was the most successful conference I've attended in a long time and find me a world leader who didn't think it was," Biden added.