Forming a more perfect union "requires all Americans to realize that your dreams do not have to come at the expense of my dreams," said the Illinois senator running to be the first black president.
"This union may never be perfect, but generation after generation has shown that it can always be perfected," he said.
In his most pointed speech of the campaign, Obama confronted the nation's legacy of racial division head on, tackling black grievance, white resentment and the uproar over his former pastor's incendiary statements. Drawing on his half-black, half-white roots as no other presidential hopeful could, Obama urged Americans to break "a racial stalemate we've been stuck in for years."'
"The anger is real; it is powerful; and to simply wish it away, to condemn it without understanding its roots, only serves to widen the chasm of misunderstanding that exists between the races," he said in a speech at the National Constitution Center, not far from where the Declaration of Independence was adopted.
The speech was the most racially tinged during his campaign to become the first black president, covering divisions from slavery to the O.J. Simpson trial to the recovery efforts after Hurricane Katrina, along with his own background. Obama rarely talks so openly about his race in such a prominent way, but he recognized it has been a major issue in the campaign that has taken a "particularly divisive turn" in the last few weeks as video of his longtime pastor spread on the Internet and on television.
Obama's advisers say the candidate decided on Saturday to make the speech and spent much of Sunday and Monday writing it, finishing shortly before he took the stage. They said Philadelphia was chosen not because it has the highest concentration of blacks in Pennsylvania, the next state to vote on April 22, but because of its historical significance.
Obama said sermons delivered by his longtime pastor, the Rev. Jeremiah Wright, "rightly offend white and black alike." Those sermons from years ago suggested the United States brought the Sept. 11 terrorist attacks on itself and say blacks continue to be mistreated by whites.
While Obama rejected what Wright said, he also embraced the man who inspired his Christian faith, officiated at his wedding, baptized his two daughters and has been his spiritual guide for nearly 20 years.
"I can no more disown him than I can disown the black community," Obama said, speaking in front of eight American flags. "I can no more disown him than I can my white grandmother -- a woman who helped raise me, a woman who sacrificed again and again for me, a woman who loves me as much as she loves anything in this world, but a woman who once confessed her fear of black men who passed by her on the street, and who on more than one occasion has uttered racial or ethnic stereotypes that made me cringe."
Obama said he knew Wright to occasionally be a fierce critic of U.S. policy and that the pastor sometimes made controversially remarks in church that he disagreed with, but he said he never heard Wright talk about any ethnic group in derogatory terms. The comments that have become a source of debate recently "were not only wrong but divisive" and have raised questions among voters, he said.
"I confess that if all that I knew of Reverend Wright were the snippets of those sermons that have run in an endless loop on the television sets and YouTube, if Trinity United Church of Christ conformed to the caricatures being peddled by some commentators, there is no doubt that I would react in much the same way," he said. "But the truth is, that isn't all that I know of the man."
Wright said shortly after the Sept. 11 attacks: "We have supported state terrorism against the Palestinians and black South Africans, and now we are indignant because the stuff we have done overseas is now brought right back to our own front yards. America's chickens are coming home to roost."
In a 2003 sermon, he said blacks should condemn the United States.
Obama said he came to Wright's church because he was inspired by Wright's message of hope and his inspiration to rebuild the black community.
Obama said Wright's comments have sparked a discussion that reflect complexities of race in the United States that its people have never really resolved.
"We do not need to recite here the history of racial injustice in this country," Obama said. "But we do need to remind ourselves that so many of the disparities that exist in the African-American community today can be directly traced to inequalities passed on from an earlier generation that suffered under the brutal legacy of slavery and Jim Crow."
Obama said anger over those injustices often find voice in black churches on Sunday mornings. "The fact that so many people are surprised to hear that anger in some of Reverend Wright's sermons simply reminds us of the old truism that the most segregated hour in American life occurs on Sunday morning," he said.
Obama argued that the anger often distracts from solving real problems and bringing change. But he said it also exists in some segments of the white community that feels blacks are often given an unfair advantage through affirmative action.
"If we walk away now, if we simply retreat into our respective corners, we will never be able to come together and solve challenges like health care, or education, or the need to find good jobs for every American," Obama said, drawing a rare burst of applause in a somber address.
An Associated Press-Yahoo News poll conducted in January found 15 percent of whites said they have at least a somewhat unfavorable impression of blacks, while 26 percent expressed a favorable impression. Among blacks, 7 percent had an unfavorable impression of whites, while 49 percent have a favorable impression.
"In the white community, the path to a more perfect union means acknowledging that what ails the African-American community does not just exist in the minds of black people; that the legacy of discrimination -- and current incidents of discrimination, while less overt than in the past -- are real and must be addressed," Obama said.