US President Joe Biden will transfer power to Vice President Kamala Harris while he is under anaesthetic for a routine colonoscopy.
The procedure is part an annual health check-up, but as the oldest president to occupy the Oval Office, Biden’s health is a greater source of interest for the media and constitutional experts than that of some of his predecessors.
Today, Harris will become the first woman in history, if only for a brief period of time, to be vested with the full powers of the President of the United States.
"The Vice President will work from her office in the West Wing during this time," White House press secretary Jen Psaki said in a statement.
Presidential power is routinely transferred to the vice president when the president is incapacitated.
President George W Bush had colonoscopies in 2002 and 2007, and transferred power to Dick Cheney, his Vice President at the time.
The transfer occurring today adheres to this long established procedure outlined in the constitution, Ms Psaki said.
Mr Biden, who will enter his 79th year on Saturday, has said he intends to run alongside Harris to get a second presidential term in 2024.
Before being picked as Biden’s running mate, Harris, 57, made an unsuccessful bid for the Democratic Party nomination in 2020.
Biden is a teetotaller, doesn’t smoke, and is thought to be in good physical condition.
In December 2019, Mr Biden was described by his doctor as "a healthy, vigorous, 77-year-old male, who is fit to successfully execute the duties of the presidency."