Washington DC - President Joe Biden urged Americans on Wednesday to "stand guard" against threats from oligarchs, disinformation, and AI in a future under Donald Trump as he delivered a dark farewell address ahead of stepping down next week.

Biden, who will be succeeded by Trump on Monday, touted his achievements in steering the US economy out of the deep crisis inflicted by the Covid-19 pandemic and said he had made the nation's alliances abroad stronger.

However, in his brief Oval Office speech on live television, the Democrat quickly turned to painting a series of dangers facing the US.

Clearly referring to Trump's close ties to the world's richest man Elon Musk and other tech tycoons, Biden said an "oligarchy is taking shape in America" – and "a dangerous concentration of power."

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He said the ultra-rich around Trump represents a concentration of "extreme wealth, power, and influence that literally threatens our entire democracy."

Biden recalled the stark warning issued by President Dwight Eisenhower in his own farewell address in 1961 about the dangers of an out-of-control military-industrial complex.

"I'm equally concerned about the potential rise of a tech industrial complex," he said, adding that a "crumbling" media means Americans are increasingly vulnerable.

"Americans are being buried under an avalanche of misinformation and disinformation, enabling the abuse of power," the outgoing president said.

Also clearly referring to Trump's plans to roll back environmental protections and withdraw from a major international global accord on combating global warming, Biden said that "powerful forces want to wield their unchecked influence to eliminate the steps we've taken to tackle the climate crisis, to serve their own interest for power and profit."

Naming another increasingly global challenge, Biden said artificial intelligence "is the most consequential technology of our time" that could bring huge benefits but also poses "risks for our economy and our security, our society."

Signing off before Trump returns for a second term on January 20, Biden told Americans: "Now it's your turn to stand guard."