In a break with tradition, Barack Obama will accept the Democratic presidential nomination at Invesco Field at Mile High, a 76,000-seat stadium, rather than at the site of the party's national convention across town.

Democratic Party officials said the decision to move Obama's speech on the final night of the Aug. 24-28 convention to the giant open-air football field of the Denver Broncos was a natural extension of the Illinois senator's efforts to open up the political process.

In a conference call with reporters, DNC Chairman Howard Dean said he was "delighted" about the change in venue for the convention speech. He batted away questions about logistical challenges and added costs the change would produce, saying those things would be worked out in the coming weeks.

"This is very much in keeping with Senator Obama's philosophy and, I might add, my philosophy as well," Dean said of moving the speech. "I think it's very fitting, especially the way Sen. Obama got here with his enourmous grassroots operation."

Separately, one official confirmed that Obama's aides were attempting 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.

The Gate was the site of one of Ronald Reagan's most memorable speeches. On a trip in July 1987, Reagan stood before throngs of West Berliners and implored then Soviet President Mikhail Gorbachev to tear down the Berlin Wall dividing the city. The wall is no longer there.

Dean also acknowledged the change of venue for the convention speech would raise security challenges, but said he and Denver Mayor John Hickenlooper had agreed such challenges won't deter the move.

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

"We're used to this type of thing," he said, citing baseball games where the president throws out the first pitch.

Most of the convention will take place at the 21,000-seat Pepsi Center. Construction for the convention was beginning there Monday amid concerns about lagging fundraising 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 Obama campaign's help to close the gap.

Dean insisted the convention was operating on budget and the fundraising was proceding apace _ a vew echoed by Obama senior adviser Anita Dunn, who said the campaign was on board to help.

"We're working as a team here," Dunn said. "The fact that the nomination was not decided until the begining of June, clearly many donors would have hung back a little to see if the candidate of their chioice was going to get the nomination."

With a heavy influx of younger voters and Hispanics in recent years, Colorado, once heavily Republican, is one of a handful of states in the mountain West that have been trending more Democratic. Both parties view it as a general-election swing state; Republican John McCain kicked off a five-day economy-focused campaign swing in Denver Monday.

The Obama sought to capitalize on the announcement of the new speech venue in a fundraising e-mail to supporters Monday.

"We're going to kick off the general election with an event that opens up the political process the same way we've opened it up throughout this campaign. Barack has made it clear that this is your convention, not his," campaign manager David Plouffe wrote.

The campaign will choose 10 people who contribute at least $5 to the campaign between now and July 31 to fly to the convention and meet Obama backstage before the speech, Plouffe added.

Obama is known for drawing huge crowds to many of his speeches. In May, a record 75,000 jammed into a riverside park in Portland, Ore., to hear him speak shortly before that state's primary.

Obama is scheduled to deliver his acceptance speech on Thursday, Aug. 28, the fourth and final night of the convention. It coincides with the 45th anniversary of Martin Luther King Jr.'s "I Have a Dream" speech on the steps of the Lincoln Memorial in 1963.

The Illinois senator is running to be the first black president.

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Associated Press Writers David Espo in Washington and Ivan Moreno in Denver contributed to this report.