U.S. President Joe Biden on Sunday dropped his reelection bid, after a growing number of Democrats expressed concerns over his viability as a candidate following a disastrous debate performance late last month.

"While it has been my intention to seek reelection, I believe it is in the best interest of my party and the country for me to stand down and to focus solely on fulfilling my duties as President for the remainder of my term," Biden said in a statement posted on X.

He said he will speak to the nation later this week in more detail about his decision.

In another post, Biden offered his full support and endorsement for Vice President Kamala Harris to be the Democratic nominee. "Democrats - it's time to come together and beat Trump. Let's do this," he wrote.

Biden's announcement, which ended weeks of speculation over his decision, came after reports emerged that a number of Democrats had urged him to step down, including prominent figures such as former U.S. President Barack Obama, former House Speaker Nancy Pelosi and Senate Majority Leader Chuck Schumer.

A sitting U.S. president and presumptive nominee has never dropped out of the race this late in the election process before. Biden's decision highlights the gravity of the crisis his campaign faced following the debate against former President Donald Trump, who formally accepted the Republican nomination on Thursday.

In the weeks following the debate, the president attempted to push back, asserting his commitment to remain in the race through various public appearances and meetings with Democratic officials. Even on Saturday, he posted on X that it's the most important election of Americans' lifetimes, and "I will win it."

According to the latest Real Clear Politics poll averages, Trump leads Biden in all the key battleground states, including key swing states Wisconsin, Michigan and Pennsylvania.