Joe Biden's 'Battle Box' Gaffe During Speech After Trump Rally Shooting

As the US reeled from images of a bloodied Donald Trump waving his fist after the gunman opened fire at a campaign rally in Pennsylvania yesterday, Joe Biden - in his address to the nation - called for unity and said that American politics "must never be a literal battlefield".

While he appeared to start off well, the US President soon began to stumble over his words.

During his speech, Joe Biden inadvertently referred to resolving differences at the "battle box" instead of the "ballot box."

Democrats are closely watching the president following a disastrous debate performance and a series of gaffes, renewing concerns about his age and ability to govern.

Joe Biden last week introduced Ukraine President Volodymyr Zelenskyy as his Russian rival Vladimir Putin.

"And now I want to hand it over to the president of Ukraine, who has as much courage as he has determination, ladies and gentlemen, President Putin," he said, referring to Zelenskyy while speaking on the sidelines of the NATO Summit in Washington.

He then quickly corrected himself and said, "President Putin, you're going to beat President Putin, President Zelenskyy. I am so focused on beating Putin."

Shortly afterward, Biden made another blunder when he referred to his deputy, Kamala Harris, as "Vice President" Trump at a high-stakes news conference.

The 81-year-old has so far defied calls to step aside. Allies have warned he needs to do more to convince his party and the public that, as he insists, only he can beat Trump in the presidential race.