US President Joe Biden announced on Sunday he was stepping down from the 2024 US presidential race.

"It has been the greatest honor of my life to serve as your president," he said in an online post.

"And while it has been my intention to seek reelection, I believe it is in the best interest of my party and my country for me to stand down."

The 81-year-old president has been facing calls to resign since his debate against Donald Trump three weeks ago, where he seemed frail, was struggling to focus, and slurring his words. Before the latest statement on Sunday, however, Biden tried to project defiance and repeatedly dismissed those calls. 

Biden endorses Kamala Harris

While confirming he would not be running against Trump at the November election, Biden indicated he would be staying on as president until the end of his term. The president also thanked his Vice President Kamala Harris for being an "extraordinary partner."

Soon after, Biden also endorsed Harris as the next Democratic nominee.

If the Democrats align behind Harris, it would avoid a complicated and potentially acrimonious process within the party to find a new candidate and mount their own campaign to challenge Trump.

Biden boasts political achievements

Biden is the oldest man to serve as US president. If elected again, Trump would become the second-oldest person to serve as president.

Biden's advanced age has prompted concerns about his mental acuity and ability to lead.

In his message, however, Biden drew attention to his achievements in office, praising "historic investments" in rebuilding the US and unprecedented climate legislation.

"America has never been better positioned to lead than we are today," he said.

dj/ab (Reuters, AFP, AP, dpa)