Democrat Joe Biden has been certified as the winner of the presidential election in Pennsylvania, the US state’s governor said.

Governor Tom Wolf, a Democrat, tweeted that the Pennsylvania State Department “certified the results of the November 3 election in Pennsylvania for president and vice president of the United States.

“As required by federal law, I’ve signed the Certificate of Ascertainment for the slate of electors for Joe Biden and Kamala Harris.”

President Donald Trump, who lost the state’s 20 electoral votes to Mr Biden, has made Pennsylvania a centrepiece of his unsuccessful legal attempts to invalidate the election results.

Mr Trump had won the state in 2016 against expectations against Democrat nominee Hillary Clinton.