US President-elect, Joe Biden, is forging ahead with his transition despite Donald Trump’s refusal to acknowledge defeat.

He has now named Ron Klain, a seasoned Democratic operative, as Chief of Staff in his first public White House personnel choice, according to CNN.

Biden tapped longtime aide Klain, who previously served as his first chief of staff when he was vice president.

Biden said in a statement: ''Ron has been invaluable to me over the many years that we have worked together, including as we rescued the American economy from one of the worst downturns in our history in 2009 and later overcame a daunting public health emergency in 2014.''

“His deep, varied experience and capacity to work with people all across the political spectrum is precisely what I need in a White House chief of staff as we confront this moment of crisis and bring our country together again.''

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He confirmed the appointment after visiting the Korean War Memorial in Philadelphia earlier on Wednesday, for a solemn wreath-laying ceremony to mark Veterans Day in the US.

This comes amid reports that President Donald Trump has blocked government officials from cooperating with Biden’s team in preparation for a transition.

Klain praised Biden in his own statement Wednesday, calling his new role "the honor of a lifetime."

Klain tweeted: "I look forward to helping him and the Vice President-elect assemble a talented and diverse team to work in the White House, as we tackle their ambitious agenda for change, and seek to heal the divides in our country."

"I've seen so many kind wishes tonight on this website. Thank you - and I'm sorry I can't reply to each of you. I'm honored by the President-elect's confidence and will give my all to lead a talented and diverse team in a Biden-Harris WH."