US Vice-President Kamala Harris became the first woman to – briefly – be given presidential powers while Joe Biden underwent a regular health check.
President Biden transferred power to Ms Harris for about 85 minutes, while he was placed under anaesthesia for a routine colonoscopy.
The medical examination was Mr Biden’s first as president and came on the eve of his 79th birthday.
Ms Harris temporarily took control of the US military and nuclear weapons.
She carried out her duties from her office in the West Wing of the White House, officials said.
Ms Harris, 57, is the first woman – and the first black and South Asian American – to be elected US vice-president.
White House Press Secretary Jen 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.
BBC