When his inaugural address on January 20, Biden was expected to transmit the message of national unity, but it was not allowed to be a cliché call.

Capitol Hill, where the US President-elect is about to deliver his speech, saw an unprecedented riot two weeks ago where a crowd of President Donald Trump's supporters stormed in to try to overturn the election results.

"In the eyes of many people around the world, this four-year ceremony that we consider common sense is nothing more than a miracle," President Ronald Reagan declared in his inaugural address in 1981.

This year, Biden will likely have to break 150 inauguration traditions when he cannot turn to his predecessor sitting right behind to thank him for making a smooth transfer of power.

Trump has not even congratulated Biden, the transition of power between the two administrations has been very difficult and no one can describe it as "in peace".

All these combined give Biden an "unprecedented" challenge in his inaugural address, NPR commentator Tamara Keith from NPR said.

"There is no pattern that Biden can follow in his current position," said Jeff Shesol, the historian who gave a speech to former President Bill Clinton.

Details of Biden's speech are still confidential.

In 1933, in his inaugural address, former President Franklin Delano Roosevelt frankly acknowledged the terrible devastation of the Great Depression.

"A series of unemployed citizens face a grim survival problem and an equally large number are struggling with volatile income. Only stupid optimists can deny today's dark realities.

Biden will have to speak to the country as most Republicans say they don't believe the 2020 election results are accurate.

In 2001, former President George W. Bush faced the same challenge when delivering his inaugural address while many Americans were still indignant after a controversial election that resulted in only a few.

"Sometimes our differences are so profound, it seems like we live on the same continent, not one country," Bush stressed in his inaugural address, while also thanking his opponents for challenging.

Biden also now has to deal with deep rifts in American society exposed after last summer's racial equality and now the Capitol Hill riots.

Presidential historian Russell Riley said that the years 1968-1969 can be compared with the present context.

"It was a divided country and Nixon understood well that his primary mission was healing," commented Riley of the University of Virginia's Miller Center.

In his 1969 speech, Nixon urged the American people to summon better versions of their own angels.

"We are caught in war, wanting peace. We are torn apart by divisions, wanting unity," Nixon said.

Although Biden's mission was a unique challenge, inauguration speeches almost always contained the message of healing.

"The founders place a lot of responsibility on an inaugural president with a duty of national unity, when the country is divided and deeply hurt as it is today," said historian Michael Beschloss.

The theme of Biden's inauguration was "United America," but in his remarks last week he admitted it was obvious that America was divided.

According to speech writer Shesol, in his speech, Biden will face a complicated dilemma.

"He needed to bring the Americans together, but he also had to prove that he wasn't too naive," Shesol said.