Joe Biden was caught on camera barking at staff during a tense moment as he addressed visiting world leaders.
The 81-year-old president demanded: “Who’s next?” while introducing leaders from Australia, India, and Japan at his residence in Wilmington, Delaware, yesterday evening.
The three countries, together with the US, are all participants in the Quadrilateral Security Dialogue, dubbed the Quad.
After finishing his speech about the Quad’s efforts in the fight against cancer, Mr Biden said: “I want to thank you all for being here. And now, who am I introducing next?”
After an uncomfortable pause, Mr Biden, 78, asked sharply, “Who’s next?”
An aide was then seen gesturing towards the stage before a compere introduced Indian Prime Minister Narendra Modi.
Mr Biden seemed to regain composure, cracking a joke before placing his arm around Modi.
The outgoing president is well-known for his verbal slip-ups, sometimes attributed to his age. However, Saturday’s incident is more likely to be the result of a logistical oversight than his advancing years.
The summit was part of the President’s ‘cancer moonshot’ initiative, which aims to see the US collaborate with the other Quad nations to combat the disease.
Also in attendance were Australian Prime Minister Anthony Albanese and Japanese Prime Minister Fumio Kishida.
The Quad, originally formed in 2007, was designed to counter China’s growing influence in the Indo-Pacific region. Its next meeting will occur under the leadership of whoever wins the upcoming presidential election between Kamala Harris and Donald Trump.
Mr Biden announced his decision to step down in July, following a disastrous debate in June against Mr Trump during which he frequently lost track of his thoughts and struggled to remain coherent.
As the oldest president in US history, Mr Biden has faced frequent analysis for on-stage errors and his physical decline, including several stumbles while boarding Air Force One and his stiff walk.
Senior Democrats, including Nancy Pelosi, pressured Mr Biden to step aside, fearing he would not be able to defeat Trump in a general election.
Vice President Kamala Harris’ nomination as the Democratic presidential candidate has revitalised the party’s campaign.
Her candidacy also appears to have rattled Donald Trump, as the 78-year-old Republican leader can no longer capitalise on Mr Biden’s perceived lack of energy.
Polls suggest that the race is on a knife edge ahead of the election on November 5.