President Joe Biden has cemented the Democratic Party's elevation of Kamala Harris to lead the fight for the White House against Republican Donald Trump with a convention speech that praised his vice-president as the best hope for preserving American democracy.
Biden took centre stage on the opening night of the Democratic National Convention, drawing an extended standing ovation from the party faithful and delivering a farewell speech to the party he has served for half a century - even with five months left in office.
Wiping away tears after being introduced by his daughter Ashley, Biden waved to the crowd that held signs saying "We (heart) Biden". Beaming, he responded: "I love you."
"Are you ready to vote for freedom? Are you ready to vote for democracy and for America? Let me ask you, are you ready to elect Kamala Harris and Tim Walz?" Biden said on Monday.
Taking multiple swipes at Trump, Biden promised to be the "best volunteer" Harris and Minnesota Governor Walz, her vice-presidential running mate, had ever seen.
Biden's address in Chicago kicked off a four-day event fuelled by enthusiasm for Harris and relief that Biden abandoned his own re-election bid and endorsed her to replace him.
The president's reluctant decision to step aside on July 21 came after heavy pressure from party leaders who worried the 81-year-old incumbent was too old to win or serve four more years.
Biden said “I made a lot of mistakes in my career but I gave my best to you” and "I love the job but I love my country more", drawing chants of "We love Joe".
Biden, who was No.2 to the nation's first Black president, Barack Obama, is urging Democrats to unite behind a candidate who, if triumphant on November 5, would become the first woman, who is also Black and South Asian, to be elected US president.
Harris is riding a historic whirlwind into the convention: her campaign has broken fundraising records, packed arenas with supporters, and turned some opinion polls in Democrats' favour.
She joined Biden onstage for a hug after his address on Monday.
Biden had hoped a month ago to deliver a speech later this week to accept the Democratic nomination for another four-year term.
Instead, he will travel to California for a holiday.
Biden dropped his re-election bid after his disastrous debate performance against Trump on June 27 prompted longtime allies, major donors and other party supporters to demand he step aside.
In his speech, Biden touted his administration's accomplishments - boosting the US economy and strengthening US alliances abroad - and made the case for Americans to elect Harris as his White House successor.
He condemned the racism and white supremacy that continue to plague America, saying they had no place in the nation.
He contrasted Harris the prosecutor with Trump, a convicted felon, and catalogued what he called the former president's foreign policy failures, accusing him of bowing down to Russian President Vladimir Putin and leaving NATO in tatters.
Biden rapped Trump for calling the United States a failing nation.
"He’s the loser," Biden said with fervour.
Biden acknowledged the anger of thousands of pro-Palestinian protesters that gathered outside the convention hall, saying he has been working non-stop to achieve a ceasefire.
Thousands of protesters - but fewer than the tens of thousands organisers had predicted - assembled to pressure delegates to drop the party's military support for Israel's Gaza offensive.
Earlier, Harris, 59, made a surprise appearance, drawing cheers as she vowed to defeat Trump.
"Let us fight for the ideals we hold dear and let us always remember, when we fight we win!" Harris said to the roar of the crowd.
She will formally accept the nomination on Thursday.
Democrats also cheered their failed 2016 presidential candidate, Hillary Clinton, whose loss to Trump in 2016 dashed hopes of installing the first woman in the White House.
"The story of my life and the history of our country is that progress is possible, but not guaranteed," said Clinton, who also lost her bid for the 2008 nomination to Obama.
"And now, we are writing a new chapter in America's story.
"Kamala has the character, experience and vision to lead us forward."
