US President Joe Biden pledged a peaceful transfer of power Thursday after Donald Trump's stunning US election win.

Biden, 81, urged Americans in a solemn televised address to "bring down the temperature," in stark contrast to Trump's refusal to accept his 2020 election defeat.

As Trump began to work at his Florida resort on his transition team, Biden said he would work for an "orderly" transfer of power.

In his speech from the Rose Garden of the White House, he called for unity while urging Democrats not to lose hope, saying: "Remember, a defeat does not mean we are defeated."

Yet finger-pointing has already erupted in the party over Biden's initial decision to run for a second term despite his age, before dropping out at the last minute in July and handing the reins to Harris, his vice president.

The White House denied Biden had any regrets. "He believed it was the right decision to make at that time," Press Secretary Karine Jean-Pierre said. (AFP)