"I only have one regret, that he's not here," Biden said on Tuesday, referring to his son Beau, a former attorney-general who died of brain cancer in 2015.

"Because we should be introducing him as president."

Biden choked up during the speech in Delaware, the state Biden represented as a senator for over three decades.

"Excuse the emotion, but when I die, Delaware will be written on my heart," the 78-year-old Biden added.

The speech in the city of New Castle was a send-off event for Biden as he heads to Washington to be inaugurated as the 46th president.

Biden has long been known as a politician open to displays of emotion, especially after multiple family tragedies.

His penchant for self-reflective and sometime tearful rhetoric stands in stark contrast to President Donald Trump whose speeches are best known for fiery attacks on the media and political opponents.

The inauguration has been beset by security concerns after supporters of the outgoing president attacked the Capitol building earlier this month. Thousands of troops in the National Guard have been deployed to the capital city.

Trump said he would not attend the inauguration, becoming the first president to break with tradition in over 150 years.

Australian Associated Press