The two spoke on condition of anonymity because nothing has been confirmed.
Obama campaign spokeswoman Shannon Gilson said no decisions have been made.
Representatives for the convention host committee and Mayor John Hickenlooper declined to comment or said they did not know about the proposal. Colorado Democratic Party Chairwoman Pat Waak did not return a telephone message seeking comment.
Associated Press writers P. Solomon Banda and Catherine Tsai
Democratic National Convention Committee spokeswoman Natalie Wyeth said, "There's nothing to announce."
The convention will be held Aug. 25-28 at the Pepsi Center, with Obama scheduled to accept the Democratic presidential nomination on the final night, which also is the 45th anniversary of Martin Luther King Jr.'s "I Have a Dream" speech on the steps of the Lincoln Memorial in Washington in 1963.
Obama would be the first black nominee of a major political party.
The Pepsi Center's Web site says it can hold 21,000 people for special events. Invesco Field at Mile High, where the Denver Broncos play, seats more than 76,000.