Democratic Party chairman Howard Dean acknowledged that the decision to move Obama's speech on the final night of the Aug. 25-28 convention to Invesco Field at Mile High Stadium would raise security challenges, but said he and Denver officials had agreed such concerns won't deter the change in venue.

Dean, in a conference call with reporters, also batted away questions about logistical challenges and added costs that the change would produce, saying those would be worked out.

Obama, speaking to reporters in St. Louis, said he was excited about the move.

"Sometimes our conventions don't feel like they are open to everybody," he said. "For us to be able to do it in Invesco Field is an opportunity for 80,000 people who might otherwise not have been able to participate to get involved."

Matt Burns, a spokesman for the Republican convention, dismissed the new speech locale as "stagecraft and theatrics" that "isn't the kind of change the American people deserve or expect."

It won't be the first time a presidential candidate has accepted the nomination in a stadium. On July 15, 1960, John F. Kennedy gave his acceptance speech before tens of thousands at the Los Angeles Coliseum.

Separately, one official confirmed that Obama's aides were trying to arrange a speech at a second dramatic venue: Berlin's Brandenburg Gate, part of Obama's July trip to Europe and the Middle East.

Ron Perea, Secret Service special agent in charge in Denver, declined to discuss what security precautions the agency would take for the convention's open-air event, including any restrictions on airspace and traffic.

Most of the convention will take place at the 21,000-seat Pepsi Center, where Denver's NBA and NHL teams play. Construction for the convention began there yesterday amid concerns about lagging fund-raising and cost overruns.

Last month, the convention's host committee reported it was nearly $12 million short of the $40.6 million it had pledged to raise for the effort. Host committee members spoke openly of needing the help of Obama's campaign to close the gap.

Dean said the convention was operating on budget, and Obama senior adviser Anita Dunn said the campaign was on board to help.

"The fact that the nomination was not decided until the beginning of June - clearly many donors would have hung back a little to see if the candidate of their choice was going to get the nomination," Dunn said.

Obama is known for drawing huge crowds to many of his speeches. His address on the final night of the convention will coincide with the 45th anniversary of the Rev. Dr. Martin Luther King Jr.'s "I Have a Dream" speech in 1963.