Video report by ITV News Washington Correspondent Robert Moore
Joe Biden wiped away tears as he made a farewell speech to Delaware, in which he paid tribute to his late son Beau.
Mr Biden, who arrived in Washington on Tuesday ready for his inauguration the next day, made his emotional speech at the National Guard headquarters in Delaware, which was named for his son.
Speaking before he left for Washington, Mr Biden, his voice thick with emotion, told the crowd: "I am proud, proud, proud, proud to be a son of Delaware. And I am even more proud to be standing here doing this from the Major Beau Biden facility. Ladies and gentlemen, I only have one regret: he's not here.
"Because he should... we should be introducing him as president.
"But we have great opportunities. Delaware has taught us anything's possible. Anything's possible in this country. So may God bless you all and may God protect our troops. Thank you."
Mr Biden also talked about making change in America and the enormity of having a black and Asian vice president.
He said: "Twelve years ago, I was waiting at the train station in Wilmington for a black man to pick me up on our way to Washington, where we were sworn in as president and vice president of the United States of America. And here we are today.
Farewell address of President Donald Trump
"My family and I, about to return to Washington to meet a black woman of south Asian descent, to be sworn in as president and vice president of the United States.
"As I told Beau on that station waiting for Barack and Hunter and Ashley, I said, 'don't tell me things can't change. They can and they do.' That's America. That's Delaware."
The event was attended by about 100 people, including numerous Delaware elected officials and members of Mr Biden's family.
After leaving Wilmington, Mr Biden flew to Washington where he attended a memorial for the US's 400,000 Covid-19 victims.
He will spend the night at Blair House, the president's official guest house, before moving into the White House after he is sworn in on Wednesday.
Mr Biden plans to issue a series of executive orders on his first day as president — including reversing Donald Trump’s effort to leave the Paris climate accord, canceling his travel ban on visitors from several predominantly Muslim countries, and extending pandemic-era limits on evictions and student loan payments.
Mr Trump will not be attending Biden's inauguration, the first outgoing president to skip the ceremony since Andrew Johnson more than a century and a half ago.