US President Joe Biden has defiantly rejected calls that he step aside from the presidential race against Republican opponent Donald Trump, presenting a challenge to fellow Democrats who are concerned his age will dissuade voters.

“I am running and gonna win again,” Biden, 81, told supporters in a fiery speech in Madison, Wisconsin on Friday.

He then taped an ABC News interview in which he argued he is the best Democratic candidate to prevent Trump from regaining the White House in the November 5 election and that only the “Lord Almighty” could convince him otherwise.

Biden faces an uprising within his own party to end his campaign run after the shaky and halting debate performance against Trump on June 27, which includes donors, lawmakers, some Democratic officials and strategists.

The events on Friday seemed to do little to temper some Democrats’ concerns.

In the coming days party members could decide whether to back the president or move swiftly to push him aside.

On Saturday, Vice President Kamala Harris will speak in New Orleans at the Essence Festival of Culture, an annual culture and music festival sponsored by Essence magazine, which caters to black women.

Harris has emerged as a top choice to replace Biden if he were to step aside as the Democratic Party’s standard-bearer.

Harris on Friday posted a supportive note on X, formerly Twitter, after Biden’s rally in Madison, saying the president had devoted his life to fighting for Americans.

“In this moment, I know all of us are ready to fight for him,” she said.

Some polls show Trump’s lead over Biden widening, and Democrats worry concerns about the president could weigh on down-ballot races.

Senator Mark Warner from Virginia is planning a meeting on Monday to discuss Biden’s candidacy.

Biden has no public events on his schedule on Saturday but is going to church.