U.S. President-elect Joe Biden has appointed top Democratic official Ron Klain as his chief of staff and assistant to the president.

Klain is one of Biden’s closest confidants and first worked for the Democrat in 1989 when he was a U.S. senator.

Klain has been a fierce critic of Republican President Donald Trump’s handling of the novel coronavirus pandemic.

He is expected to be a key figure in Biden’s response to the health crisis.

In this capacity, Klain will oversee the Executive Office of the President and serve as a senior advisor.

In addition to supporting the president-elect, Klain will work to build a diverse, experienced and talented team to help President-elect Biden and Vice President-elect Kamala Harris meet the urgent challenges facing the country, a media release said.

“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,” Biden said in a statement. “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.”