Obamas endorse Kamala Harris for president

Kamala Harris and Barack Obama have known each other for 20 years

Barack Obama has endorsed Vice-President Kamala Harris to be the Democratic presidential nominee, ending days of speculation over whether he would support her.

Former President Obama and ex-First Lady Michelle Obama said in a joint statement that they believe Ms Harris has the "vision, the character, and the strength that this critical moment demands".

Mr Obama was reportedly among more than 100 prominent Democrats Ms Harris spoke to after President Joe Biden announced last Sunday he was dropping out of the race.

In a statement at the time, Mr Obama praised Mr Biden's exit, but stopped short of endorsing Ms Harris.

The US vice-president has already secured the support of a majority of Democratic delegates, setting her on course to become the official nominee at the party convention in August.

The Obamas said in Friday's statement that they could not be "more thrilled to endorse" Ms Harris. They vowed to do "everything we can" to elect her.

"We agree with President Biden," said the couple's statement, "choosing Kamala was one of the best decisions he’s made. She has the resume to prove it."

They cited her record as California’s attorney general, a US senator and then vice-president.

"But Kamala has more than a resume," the statement continued. "She has the vision, the character, and the strength that this critical moment demands.

"There is no doubt in our mind that Kamala Harris has exactly what it takes to win this election and deliver for the American people.

"At a time when the stakes have never been higher, she gives us all reason to hope."

The statement was accompanied by a video of Ms Harris taking a phone call from the Obamas in which they pledge their support.

"Oh my goodness," says the vice-president in the clip. "Michelle, Barack, this means so much to me."

Ms Harris has held a number of campaign events across the US in the days since Mr Biden withdrew from the race.

On Thursday, she addressed the American Federation of Teachers union in Houston.

While the event was billed as part of her vice-presidential duties, it had the air of a campaign rally, with loud applause and cheers from the audience.

Echoing language used in campaign events earlier in the week, Ms Harris took aim at what she termed "extremist" Republicans and "failed" policies.

“We want to ban assault weapons, and they want to ban books,” she said.

Meanwhile, Republican presidential nominee Donald Trump continued to pivot to assail his new rival.

On Friday evening, at a Florida summit for the conservative Turning Point USA organisation, he vowed to defeat Ms Harris, calling her the "most incompetent" vice-president ever.

He warned that if elected she would be "the most extreme radical liberal president in American history".

Trump has refused to commit to a televised debate with Ms Harris until she is officially confirmed as the party's nominee.

He suggested Democrats were "still holding out for someone 'better'".