WASHINGTON—A source close to the process of selecting Barack Obama’s attorney general says the president-elect has “informally” offered the post to Washington lawyer Eric Holder, who has accepted.

The person spoke on condition of anonymity Wednesday because no announcement has been made. He said that Holder has “informally” accepted the offer, pending completion of the vetting process.

Holder would be the nation’s first black attorney general. He could run into some potential political problems over a 2001 pardon of a wealthy commodities dealer by President Bill Clinton, whose administration Holder served as deputy attorney general. The trader, Marc Rich, had spent years running from tax charges.