Faced with what his advisers acknowledged was a major test to his candidacy, Senator Barack Obama sought on Monday to contain the damage from incendiary comments made by his pastor and prepared to address the issue of race more directly than at any other moment of his presidential campaign.

Though he has faced questions about controversial statements by the pastor, the Rev. Jeremiah A. Wright Jr., for more than a year, Mr. Obama is enduring intense new scrutiny now over Mr. Wright’s characterizations of the United States as fundamentally racist and the government as corrupt and murderous.

Mr. Obama, in a speech Tuesday in Philadelphia, will repeat his earlier denunciations of the minister’s words, aides said. But they said he would also use the opportunity to open a broader discussion of race, which his campaign has said throughout the contest that it wants to transcend. He will bluntly address racial divisions, one aide said, talking about the way they play out in church, in the campaign, and beyond.

Mr. Obama continued to write the speech on Monday evening, which he believes could be one of the most important of his presidential candidacy, aides said. His wife, Michelle, had not been scheduled to travel with him this week, but hastily made plans to be in Philadelphia.