Ms Pelosi, speaker of the House of Representatives, celebrated by saying: “We kept the republic!” before adding: “It’s a time to heal and a time to grow together.”
Mr Biden was declared the winner of the 2020 election at around 11.30am EST (4.30pm GMT) after securing Pennsylvania, taking him well over the required 270 electoral votes.
Speaker Pelosi, a longtime friend and supporter of Mr Biden, is an outspoken critic of Mr Trump and the two have clashed many times. The Democrat spearheaded Mr Trump’s impeachment process.
Ms Pelosi was the first senior government official to refer to Mr Biden as the “president-elect” at a press conference on Friday.
Mr Obama called the win “historic” and “decisive” in a statement, while Ms Clinton defiantly said: “It's a history-making ticket, a repudiation of Trump, and a new page for America.”
Mr Biden will be sworn in as the 46th US president on 20 January, while Senator Harris will make history as the first-ever female vice president.
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