Watch: As Joe Biden seems to fall asleep at the COP26, Twitter takes aim at him

US President Joe Biden was accused of sleeping during the opening sessions of the COP26 climate summit in Glasgow, Scotland, by Twitter users.

When a speaker said that the world leaders gathered for the conference have the "power to make decisions and reach agreements that will affect the lives of generations to come," Biden appeared to close his eyes for about 20 seconds, according to a video clip first shared by a reporter for The Washington Post.

Biden’s eyes closed for a few seconds before he woke himself. However, seconds later, they shut down again for a second time.  

An assistant then approached Biden and began whispering to him, who turned his head to listen momentarily before returning to the speech. 

Before applauding the opening speaker, the US president uncrossed his arms and listened to what the staff member had to say. 

Watch | US President Joe Biden speaks at the G20 summit in Rome

Biden, who is 78 years old, is the oldest person to serve as president of the United States, and opponents, notably former President Donald Trump and his followers, have speculated about his health and mental fitness for the office.

Trump regularly accused Biden of becoming senile during his unsuccessful re-election campaign in 2020, citing his occasionally halting speech, which is the result of a long-documented stuttering condition. 

(With input from agencies)