Philadelphia: Barack Obama's first major speech on race drew praise for its eloquence on Tuesday - but Republicans think he handed them a major weapon by refusing to disown family pastor Jeremiah Wright, who is known for racially inflammatory remarks.

"This is far and away the most damaging issue of the campaign for him, and his wonderful speech did nothing to make it go away," said Whit Ayres, a Republican pollster.

Obama, whose victories in mostly white states such as Iowa and Wisconsin were powered by a multiracial coalition, has been on the defensive after release of a video showing Wright's sermon on racism.

Obama has tread lightly on the issue of race for fear of being marginalised as a "black candidate." And it was a measure of his anxiety over the Wright controversy that he addressed race during Tuesday's hastily scheduled speech in the shadow of Constitution Hall.

Obama began by distancing himself from the firebrand pastor, who also has made controversial remarks about Israel, Aids and the September 11, 2001, attacks, while praising Nation of Islam founder Louis Farrakhan.

Distorted view

Wright's views "denigrate both the greatness and the goodness of our nation" and "rightly offend white and black alike," he said, adding that the pastor had "a profoundly distorted view of this country."

Obama, flanked by eight American flags, seemed uneasy rebuking a friend who had officiated at his wedding, baptised his daughters and furnished the phrase "Audacity of Hope" for his most recent bestseller.

But while deploring Wright's words, Obama exalted the man, portraying his rage as an understandable product of his experiences with Jim Crow, segregation and racial injustice. "I can no more disown him than I can disown the black community," Obama said. "I can no more disown him than I can my white grandmother, 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."

The handpicked audience of 200 at the National Constitution Centre applauded and some dabbed tears from their eyes.

Hillary Clinton, speaking to reporters at an event a few blocks away, praised the speech. "I'm very glad that he gave it. It's an important topic," she said, adding, "race and gender are difficult issues."

But Republicans pounced on the speech, saying Obama's measured criticism didn't go far enough and promising to invoke Wright early and often should Obama win the nomination.

"I think it's an obligation of any opponent to use this issue, to make Reverend Wright a centrepiece of the campaign," said Representative Peter King, Republican-New York. "His speech was disappointing and shameful," King added. "... This goes to the heart of who Barack Obama is. He's trying to say he represents the 21st-century view on race, and here he's sticking up for this guy."

Contradiction

Added pollster Ayres: "The problem is the contradiction between the fundamental message of the Obama campaign about bringing America together and Wright's hate-filled, divisive message." Wright himself anticipated Republican attacks, telling The New York Times in April: "If Barack gets past the primary, he might have to publicly distance himself from me. ... I said it to Barack personally, and he said, 'Yeah, that might have to happen'."

Even before Wright's comments were made public, Obama was having trouble gaining traction with white, working-class voters, a group Clinton dominated in her victory in the March 4 Ohio primary.

And his association with the pastor seems to be hurting him more broadly: A national CBS poll released on Tuesday found that 36 per cent of independents who had heard about Wright's comments said they reflected negatively on Obama.

In a frank and nuanced assessment of racial prejudice, Obama told his predominantly black audience that Americans needed to recognise the legitimate causes of white and black working-class anger before the country could move beyond historical racial divisions.