PHILADELPHIA Senator Barack Obama renewed his objection to the controversial statements delivered by the longtime pastor of his Chicago church, but declared in a speech here Tuesday that it was time for America to move beyond some of our old racial wounds.

Its a racial stalemate weve been stuck in for years, Mr. Obama said. Contrary to the claims of some of my critics, black and white, I have never been so naïve as to believe that we can get beyond our racial divisions in a single election cycle, or with a single candidacy particularly a candidacy as imperfect as my own.

In an address at the National Constitution Center, a building steeped in the nations historic symbolism, Mr. Obama delivered a sweeping assessment of race in America. It was the most extensive speech of his presidential campaign devoted to race and unity, a moment his advisers conceded presented one of the biggest tests of his candidacy.

For nearly a week, Mr. Obama has struggled to distance himself from a series of controversial statements by his former pastor, the Rev. Jeremiah A. Wright Jr., who characterized the United States as fundamentally racist and the government as corrupt and murderous. Mr. Obama concluded over the weekend that he had failed to resolve the questions, aides said, and told advisers he wanted to address the firestorm in a speech.

In his address here, delivered in an auditorium to an audience of about 200 elected officials and members of the clergy, Mr. Obama disavowed the remarks by Mr. Wright as not only wrong, but divisive, divisive at a time when we need unity. But he did not wholly distance himself from his pastor or the church, Trinity United Church of Christ, on Chicagos South Side.

I can no more disown him than I can disown the black community, Mr. Obama said. I can no more disown him than I can disown 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.

Standing against a backdrop of American flags, Mr. Obama offered the most thorough explanation to date about his association with the church and his pastor, whom he has known for nearly 20 years.

For some, nagging questions remain, Mr. Obama said. Did I know him to be an occasionally fierce critic of American domestic and foreign policy? Of course. Did I ever hear him make remarks that could be considered controversial while I sat in church? Yes. Did I strongly disagree with many of his political views? Absolutely just as Im sure many of you have heard remarks from your pastors, priests or rabbis with which you strongly disagreed.

In a 45-minute address, interrupted numerous times by applause, Mr. Obama acknowledged the political risks facing his campaign, particularly as he tries to increase his appeal to white male voters here in advance of the Pennsylvania primary on April 22 and the remaining other contests.

Race is an issue that I believe this nation cannot afford to ignore right now, he said.

I suppose the politically safe thing would be to move on from this episode and just hope that it fades into the woodwork, Mr. Obama said. We can dismiss Reverend Wright as a crank or a demagogue, just as some have dismissed Geraldine Ferraro, in the aftermath of her recent statements, as harboring some deep-seated racial bias.

He spoke about his diverse upbringing, a black father from Kenya and a white mother from Kansas. He noted that his candidacy had been successful in predominantly white states and black states, but he conceded that the nations racial divisions remained firmly entrenched, a notion underscored by the polarization in the presidential campaign.

We can play Reverend Wrights sermons on every channel, every day and talk about them from now until the election, and make the only question in this campaign whether or not the American people think that I somehow believe or sympathize with his most offensive words. We can pounce on some gaffe by a Hillary supporter as evidence that shes playing the race card, or we can speculate on whether white men will all flock to John McCain in the general election regardless of his policies.

He added: Against all predictions to the contrary, we saw how hungry the American people were for this message of unity. Despite the temptation to view my candidacy through a purely racial lens, we won commanding victories in states with some of the whitest populations in the country. In South Carolina, where the Confederate flag still flies, we built a powerful coalition of African-Americans and white Americans.

Yet in recent weeks, as the Democratic nominating fight has intensified with Senator Hillary Rodham Clinton, discussions of race and gender have emerged from an underlying subtext to providing an overriding narrative of the campaign.

The comments that have been made and the issues that have surfaced over the last few weeks reflect the complexities of race in this country that weve never really worked through a part of our union that we have not yet made perfect, Mr. Obama said. And 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.