FORMER US PRESIDENT BARACK OBAMA

Obama says he "could not be prouder" to congratulate Biden and vice president-elect Kamala Harris.

In a statement on Saturday, Obama says Biden has "got what it takes to be President and already carries himself that way", because he will enter the White House facing "a series of extraordinary challenges no incoming President ever has".

Acknowledging that the election revealed the nation remains bitterly divided, Obama said, "I know he'll do the job with the best interests of every American at heart, whether or not he had their vote".

FORMER US PRESIDENT BILL CLINTON

Bill Clinton tweeted that "America has spoken and democracy has won".

The 42nd president also predicted Biden and Harris would "serve all of us and bring us all together".

FORMER US PRESIDENT JIMMY CARTER

Jimmy Carter, the 39th president, said in a statement on Saturday that he and his wife, Rosalynn, are "proud" of the Democrats' "well-run campaign and seeing the positive change they bring to our nation".

BRITISH PRIME MINISTER BORIS JOHNSON

"Congratulations to Joe Biden on his election as President of the United States and to Kamala Harris on her historic achievement," Johnson said in a statement.

"The US is our most important ally and I look forward to working closely together on our shared priorities, from climate change to trade and security."

NEW ZEALAND PRIME MINISTER JACINDA ARDERN

"The relationship between our two countries is strong, and I look forward to developing even closer relations with the incoming Biden Administration," Ardern said in a written statement on Sunday.

FRENCH PRESIDENT EMMANUEL MACRON

"The Americans have chosen their President. Congratulations @JoeBiden and @KamalaHarris! We have a lot to do to overcome today's challenges. Let's work together!" Macron tweeted.

GERMAN CHANCELLOR ANGELA MERKEL

"I look forward to future cooperation with President Biden. Our transatlantic friendship is irreplaceable if we are to master the great challenges of our time," Merkel said on Twitter.

CANADIAN PRIME MINISTER JUSTIN TRUDEAU

"I look forward to working with President-elect Biden, Vice President-elect Harris, their administration, and the United States Congress as we tackle the world's greatest challenges together," the Canadian prime minister said in a statement.

SPANISH PRIME MINISTER PEDRO SANCHEZ

"The American people have chosen the 46th President of the United States. Congratulations @JoeBiden and @KamalaHarris," Sanchez tweeted.

"We wish you good luck and all the best. We are looking forward to cooperating with you to tackle the challenges ahead of us."

Australian Associated Press