WASHINGTON — Joe Biden turned 80 on Sunday, a milestone for the already-oldest president in U.S. history as some Democrats question his intention to run for reelection in two years.

The president and his family will celebrate at a brunch organized by first lady Jill Biden at the White House.

Biden has said he intends to run for a second term in 2024 and will make a final decision early next year. He has brushed off concerns about his age and fitness to handle another campaign and potentially four more years in office.

“I’m in good health,” Biden told MSNBC’s Jonathan Capehart last month. “Everything physically about me is still functioning well. And mentally, too.”

Polls show voters — including those in his own party — have reservations about the president’s age. A November Reuters/Ipsos poll found 70% of voters agreed that the statement “too old to work in government” strongly or slightly described Biden. Among Democrats, 59% agreed.

In the same survey, 55% of all respondents said former President Donald Trump is too old for public service. Trump, who entered the 2024 race on Tuesday, turned 76 in June. Florida Gov. Ron DeSantis, the No. 2 choice of GOP primary voters in polls, is 44.

Concerns about Biden’s age coincide with a generational shift in House Democrats’ top ranks after Republicans retook the chamber. Speaker Nancy Pelosi, 82, announced last week that she will not seek reelection to leadership.

“The hour has come for a new generation to lead the Democratic caucus,” Pelosi said Thursday.

Majority Leader Steny Hoyer, 83, also said he will not seek a leadership post in the new Congress. Majority Whip Jim Clyburn, 82, did not indicate his plans but said he would back a younger slate of candidates for leadership roles.

New York Rep. Hakeem Jeffries, seen as Pelosi’s heir apparent, is 52.

Biden would be 82 on Inauguration Day in 2025.

In an interview on “The Willie Moore Jr. Show” that aired Nov. 7, the president was asked what he would say to a 50-year-old version of himself.

“That I’m still 50,” Biden said. “I can’t even say that number 80.”