Joe Biden has made a major gaff at a "high stakes" press conference tonight after appearing to confuse Ukraine's Volodymyr Zelensky for Russian President Vladimir Putin.

The President of the United States has been under the spotlight in recent days following on from his disastrous debate against Donald Trump.

With serious questions over the Democrat's cognitive ability, close attention was set to be paid tonight to a solo press conference held by the 81-year-old - his first in several months.

However, at a joint conference with Zelensky ahead of the TV address, the US President made a slip up that will have massively intensified questions about his ability to remain in the top job for another four years.

"Ladies and gentlemen, President Putin," Biden said, referring to Zelensky before correcting himself.

"Going to beat President Putin, President Zelensky. I am so focused on beating Putin," Biden said while correcting himself.