US President Joe Biden has withdrawn his candidacy for re-election, saying "it is in the best interest of my party and the country". 

The announcement came just four months before he was due to face former president Donald Trump in a rematch of the previous election.

It is understood that Biden’s poor performance in last month’s debate against Trump led to great pressure from the Democratic Party for Biden to step aside.

Following the announcement on Sunday evening, Biden endorsed vice-president Kamala Harris in the presidential race. 

He said his “first decision as the party nominee in 2020” was to select Harris, and “it’s been the best decision I’ve made”.

In a letter posted to his social media account announcing the withdrawal, he urged voters to rally behind Harris and defeat Trump in the polls.

Trump accepted the Republican presidential nomination on Thursday at the Republican National Convention (RNC) in Milwaukee, Wisconsin, amid rising calls for Biden to withdraw from the race.

‘We will fight together’

Later in a statement, Harris said she was honoured to have Biden's endorsement, adding that her "intention is to earn and win this nomination", Anadolu Agency reported.

"Over the past year, I have travelled across the country, talking with Americans about the clear choice in this momentous election.

“That is what I will continue to do in the days and weeks ahead. I will do everything in my power to unite the Democratic Party - and unite our nation - to defeat Trump and his extreme Project 2025 agenda," she said.

Kamala Harris

"We have 107 days until election day. Together, we will fight. And together, we will win," Harris wrote.

According to CNN, citing a source familiar with the issue, plans for Biden to withdraw from the race were put into action on Saturday night and finalised on Sunday.

Biden is still recovering from a Covid-19 diagnosis, resting at his home in Rehoboth Beach, Delaware.

‘Remedy the damage’

Trump said on Sunday he would "remedy the damage" he attributed to Biden shortly after the latter announced his withdrawal from the presidential race.

“Crooked Biden was not fit to run for president, and is certainly not fit to serve - And never was!” said the former president on his platform, Truth Social.

Donald Trump

The Republican presidential candidate claimed that people around Biden, including his doctor and media, knew Biden was incapable of being president.

“And he wasn’t. Now, look what he’s done to our country, with millions of people coming across our border, totally unchecked and unvetted, many from prisons, mental institutions, and record numbers of terrorists.

“We will suffer greatly because of his presidency, but we will remedy the damage he has done very quickly. Make America great again!" Trump said.

Praises for Biden

Former president Barack Obama, however, praised Biden as "one of America’s most consequential presidents" and "a patriot of the highest order".

"President Biden pointed us away from the four years of chaos, falsehood, and division that had characterised Trump’s administration," he said.

However, he fell short of endorsing Harris in his statement.

Barack Obama

Another former Democratic president Bill Clinton said Biden "has capped his extraordinary career of service with a presidency that has lifted America out of an unprecedented pandemic, created millions of new jobs, rebuilt a battered economy, strengthened our democracy, and restored our standing in the world”.

"We join millions of Americans in thanking Biden for all he has accomplished, standing up for America time and again, with his North Star always being what's best for the country," he and his wife Hillary said in a joint statement.

The Clintons endorsed Harris and said they "will do whatever we can to support her”.