Biden says he bowed out to unite nation, as Trump attacks Harris

President Joe Biden on Wednesday said dropping out of the race for the presidency and endorsing his vice president, Kamala Harris, as the Democratic candidate was the best way to unite the country, despite his ambition to win a second term.

Biden's announcement to not seek re-election on Sunday followed a disastrous June debate with Trump that exacerbated questions about his ability to win, or to serve another four years if he succeeded.

In his address to the nation from the Oval Office, he said he believed he earned reelection because of his record during his first term.

"But nothing, nothing can come in the way of saving our democracy. That includes personal ambition," he said. "So I decided the best way forward is to pass the torch to a new generation. That is the best way to unite our nation.”

Harris, the first Black woman and Asian American to serve as vice president, would become the first woman elected president if she prevails on Nov. 5. In the three days since Biden's decision, Harris has pulled in broad support across the Democratic Party and revitalised its election campaign.

Biden praised Harris as a strong leader who would make an effective president.

"She's experienced, she's tough, she's capable. She's been an incredible partner to me and a leader for our country. Now the choice is up to you the American people."

Hours earlier, Republican presidential candidate Donald Trump tried to quash some of that momentum in an aggressive speech at the rally, his first since Harris' emergence changed the race. "She is a radical Left lunatic who will destroy our country if she ever gets elected," he said.

Trump routinely uses insults in attacking his opponents and made clear he planned to ignore advice that he take a softer line. "I'm not gonna be nice!" he told his cheering supporters in Charlotte.

He attacked Harris as a driving force in the Biden administration who should be held responsible for its policies on immigration and other issues.

"I will terminate every single open border policy of the Biden Harris administration and we will seal the border and we will stop Kamala Harris invasion without delay," the former president said.

Biden put Harris in charge of working with countries in Central America to help stem the tide of migration, but she was not given responsibility for border security nor was she named "border czar."