Richardson's nomination has been all-but-announced for several weeks.
The Democratic officials, speaking on the condition of anonymity because the announcement hasn't been made, said Richardson will join Obama at a news conference in Chicago on Wednesday.
He is one of the nation's most prominent Hispanic politicians.
An energy secretary and United Nations ambassador in President Bill Clinton's administration, Richardson was a contender for the State Department job but Obama offered him the post as Commerce secretary after choosing the former first lady as his top diplomat.
Richardson sought the Democratic presidential nomination this year, but eventually dropped out and endorsed Obama.
On Monday, Obama announced his foreign and national security team, led by Clinton and the current Defense Secretary Robert Gates, a Republican. A week ago, he named his economic team, led by Timothy Geithner as treasury secretary. In the coming weeks if not days, he plans to announce former Senate Majority Leader Tom Daschle as health and human services secretary.
The upper echelon on his Cabinet now is in place.
Among those posts yet to be disclosed if not chosen: the heads of the Interior, Transportation, Labor, Energy, Housing and Urban Development, Education, Agriculture and Veterans Affairs departments. Obama also has yet to name his intelligence team, including his director of national intelligence and CIA chief.
