President Joe Biden will transfer power briefly to Vice President Kamala Harris on Friday while he is under anesthesia for a routine colonoscopy, making her the first woman to hold presidential power in U.S. history.

Biden, a Democrat, is undergoing his annual physical at the Walter Reed military hospital outside of Washington.

Harris is the first woman to serve as vice president of the United States; no woman has ever been president in the country's nearly 250-year history.

"Following the process set out in the Constitution, President Biden will transfer power to the Vice President for the brief period of time when he is under anesthesia," White House spokesperson Jen Psaki said in a statement.

"The Vice President will work from her office in the West Wing during this time," Psaki said.

Biden arrived at Walter Reed just before 9 a.m. (1400 GMT) on Friday; Harris is expected to depart for Ohio, where she's promoting the infrastructure bill, in the early afternoon.

Presidential power has been transferred to the vice president before, when President George W. Bush had colonoscopies in 2002 and 2007.

Biden, who turns 79 on Saturday, is the oldest person to take office as U.S. president, leading to high interest in his health and well-being. Although speculation has persisted about whether he will run for re-election in 2024, he has said he expects to seek a second four-year term.

Biden has pledged to be more transparent about his health than predecessor Donald Trump. The Republican visited Walter Reed in 2019 for an undisclosed reason that a former press secretary, Stephanie Grisham, later revealed was for a colonoscopy. Trump once had his doctor brief the press about the president's health after questions were raised about his mental acuity.

Psaki said the White House would release a public summary of Biden's physical later on Friday.