The cover of the biography of Steve Jobs by Walter Isaacson. (Reuters)

“I'm taking on another big writing project, so I won't be able to give the BBG the time it needs and deserves,” he said in a resignation letter sent Friday to the agency, which oversees U.S. international broadcasting, including the Voice of America and Radio Free Europe.

Isaacson, who also heads the Aspen Institute, was rumored to be among the candidates the White House had considered tapping for director of the Domestic Policy Council — a job that ultimately went to Cecilia Munoz, who had been working in the West Wing spearheading the White House’s Hispanic outreach.

Isaacson’s book “Steve Jobs” has sold an estimated 1.36 million copies in the United States alone, according to Nielsen BookScan.

The White House must now nominate Isaacson’s replacement to the eight-member bipartisan BBG board.