WASHINGTON (CNN) - Barack Obama will give his main speech of the Democratic National Convention at a 75,000-seat stadium rather than the 20,000-seat hall where the convention is taking place, convention organizers announced Monday.
Obama will accept the Democratic nomination for president at Denver's Invesco Field at Mile High on August 28.
The move is likely to put him in front of a much larger audience than normal for a political speech, even for a presidential nominee.
Democratic Party Chairman Howard Dean said Monday he did not know how much the move would add to the cost of the convention. Anita Dunn, a senior advisor to the Obama campaign, said Obama would help with fund-raising for the event.
Dean on Sunday rejected a newspaper report that the convention was over budget and facing "upwardly spiraling costs."
He issued a statement in which he said "that is false" five times in response to five claims in a New York Times article about convention planning, and he insisted again on Monday that convention planning is on track.
The party officially started preparing on Monday for the Pepsi Center to host the event, which runs August 25-28.
Convention organizers portrayed the move to Invesco Field as a reflection of Obama's success at encouraging people to vote for the first time.
"Barack Obama's campaign for change has inspired millions of Americans and brought people into the political process who might never have been involved," said the convention's co-chair, Kansas Gov. Kathleen Sebelius. "This change in the convention program will allow thousands of first-time participants a chance to take part."
Obama's largest event to date was in Portland, Oregon, in May, where he drew a crowd of approximately 75,000. He has done at least one previous stadium event, a joint appearance with talk show host Oprah Winfrey at Williams-Brice Stadium in South Carolina that drew about 29,000 people.
John F. Kennedy accepted the Democratic nomination for president in 1960 at Memorial Coliseum in Los Angeles, a 92,500-seat stadium in which an estimated 80,000 people gathered for his speech.
(Updated Monday afternoon with additional information)