WASHINGTON (Reuters) - President-elect Barack Obama is expected to nominate New Mexico Gov. Bill Richardson to head the Commerce Department, a senior Democratic source said on Tuesday.

Obama is expected to announce the appointment during a news conference scheduled for 1140 EST/1640 GMT on Wednesday in Chicago, his fifth since he began naming nominees for his Cabinet.

The appointment of Richardson, a former U.N. ambassador and energy secretary who became an Obama supporter earlier this year after dropping his own presidential bid, would make him the first Hispanic named to Obama’s rapidly filling Cabinet.

Last week Obama announced members of his economic team including his nominee for Treasury secretary, New York Federal Reserve President Timothy Geithner, and this week he unveiled his national security team including his designate for Secretary of State, New York Sen. Hillary Clinton.

Richardson, 61, had been a contender for the secretary of state post that went to his former Democratic presidential rival Clinton, but at Commerce he will play a key role in efforts to revive the faltering U.S. economy.