The temporary delegation of power to Harris made her, for a time, the first female acting president in U.S. history. Biden resumed his role as president before noon, White House press secretary Jen Psaki said.
Psaki had noted in a press statement that the same process was followed in 2002 and 2007, when then-President George W. Bush underwent the same medical procedure.
"The Vice President will work from her office in the West Wing during this time," Psaki said Friday morning.
Former President Donald Trump, 75, reportedly refused anesthesia for a medical procedure, precisely because he did not want to hand power to then-Vice President Mike Pence, according to a book from his third press secretary, Stephanie Grisham.
The White House said it will publicly share a written summary of the 78-year-old Biden's physical later Friday afternoon. Biden, the oldest president to take office, turns 79 on Saturday.
Biden's motorcade arrived at Walter Reed National Military Medical Center before 9 a.m. ET.
At 11:35 a.m., Biden spoke with Harris and White House chief of staff Ron Klain "and at that time resumed his duties," Psaki tweeted. Biden will stay at Walter Reed for the duration of his physical, she said.
In a letter to Senate President Pro Tempore Patrick Leahy, D-Vt. — the second-highest ranking official in the Senate after Harris — Biden explained, "Today I will undergo a routine medical procedure requiring sedation."
"In view of present circumstances, I have determined to transfer temporarily the powers and duties of the office of President of the United States to the Vice President during the brief period of the procedure and recovery," Biden said in the letter, which was shared by the White House in the early afternoon Friday.
"In accordance with the provisions of section 3 of the Twenty-Fifth Amendments to the United States Constitution, this letter shall constitute my written declaration that I am presently unable to discharge the powers and duties of the office of the President of the United States," Biden wrote.
"Pursuant to section 3, the Vice President shall discharge those powers and duties as Acting President until I transmit to you a written declaration that I am able to resume the discharge of those powers and duties," the letter said.
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