Obama planned to announce the nomination after Thanksgiving, according to a Democratic official familiar with the discussions. The official was not authorized to speak publicly about the negotiations and did so on condition of anonymity.
Richardson, 61, had a distinguished and visible career in Washington before returning to New Mexico, where he was elected governor in 2002. Richardson served as U.N. ambassador under President Bill Clinton and later as energy secretary. He was in the House from 1983 to 1997.
Clinton sent Richardson on several high-level diplomatic missions while he was in Congress, including direct talks with Iraqi leader Saddam Hussein.
Richardson ran for the Democratic presidential nomination but dropped out in January after a poor showing in early contests. He went on to endorse Obama at the height of the Illinois senator's primary contest with Hillary Rodham Clinton, angering many Clinton's supporters who viewed the endorsement as a disloyal snub.
Obama considered Richardson to be secretary of state and brought him to Chicago to discuss the job. The president-elect is on track to name Hillary Rodham Clinton to the top diplomatic post and was expected to announce the pick after Thanksgiving.
Obama was set to name New York Federal Reserve Bank president Timothy Geithner as his treasury secretary on Monday, in his first official Cabinet announcement. Obama also planned to name Lawrence Summers to lead the National Economic Council.
Several other candidates for Cabinet posts have emerged in recent days.
Obama's choice for attorney general is Eric Holder, who held the No. 2 slot in the Justice Department under Bill Clinton. The president-elect's aides have also encouraged speculation that Defense Secretary Robert Gates would remain in office for an interim period.
Other selections include former Senate Majority Leader Tom Daschle of South Dakota as secretary of health and human services and Arizona Gov. Janet Napolitano, likely to be named as homeland security secretary.