US Vice-President Kamala Harris will become the first woman to briefly be given presidential powers as Joe Biden undergoes his regular health check.
President Biden will transfer power to Ms Harris for the period in which he is placed under anaesthesia for a routine colonoscopy.
The medical examination will be Mr Biden’s first as president and comes on the eve of his 79th birthday.
Ms Harris will temporarily take control of the US military and nuclear weapons.
“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.
Ms Harris, 57, is the first woman – and the first black and South Asian American – to be elected US vice-president.
Ms Psaki said the temporary transfer of powers in such circumstances was not unprecedented, and that it was part of the process set out in the US constitution.
“As was the case when President George W Bush had the same procedure in 2002 and 2007,” her statement said.
Mr Biden, the oldest US president to take office, had his last full medical examination in December 2019.
At the time, his doctor released a medical report describing him as “healthy, vigorous” and “fit to successfully execute the duties of the presidency”.
The president’s latest health check comes on the day that the US House of Representatives approved his landmark $1.9tn (£1.4tn) Build Back Better Act.
The sweeping social spending and climate package is considered a key pillar of Mr Biden’s agenda.