WASHINGTON (AFP) — Democratic White House hopeful Barack Obama has quit his long-time Chicago church, following a string of racially-tinged rhetoric by preachers from its pulpit, a campaign source said Saturday.

The decision, confirmed by the official on condition of anonymity, followed the latest uproar sparked by the Trinity United Church of Christ, when a guest preacher last week mocked Obama's foe Hillary Clinton with racial rhetoric.

Obama was expected to address the controversy directly later on Saturday.

Trinity's former pastor was Reverend Jeremiah Wright, who sent the Obama campaign into turmoil when videos emerged of a string of vehement and race-based sermons emerged earlier this year.

Wright's most controversial statements, included comments assailing US and Israeli "terrorism," exhortations on blacks to sing "God damn America," over racism and allegations that AIDS was spread by the US government.

His comments, and Obama's former allegiance to the church are likely to be a major target for Republicans, should the Illinois senator as expected clinch the Democratic presidential nomination and face Senator John McCain in November's general election.

Obama on Thursday said he was "disappointed" by the latest remarks made by guest preacher, and Catholic priest Father Michael Pfleger, last Sunday at Trinity.

Pfleger mocked Clinton for appearing to cry days before the New Hampshire primary in January, saying she was on the verge of tears because "there is a black man stealing my show."

"She always thought, 'This is mine. I'm Bill's wife, I'm white and this is mine,' Pfleger said in the dramatic sermon, which now has 100,000 hits on YouTube.

"And then out of nowhere came him, Barack Obama. And she said: 'Damn, where did you come from? I'm white, I'm entitled, there's a black man stealing my show!'"

"She wasn't the only one crying, there was a whole lot of white people crying," said Pfleger, a white Catholic priest.

Obama, seeking to quell the controversy that could provide ammunition to Republican critics, quickly rejected Pfleger's rhetoric in a statement Thursday night.

"As I have traveled this country, I've been impressed not by what divides us, but by all that unites us," he said.

"That is why I am deeply disappointed in Father Pfleger's divisive, backward-looking rhetoric, which doesn't reflect the country I see or the desire of people across America to come together in common cause."

Obama initially declined to reject Wright, using the row to make a wider comment about race in America in a speech in March.

Later, however, he later repudiated his former friend, after a round of media appearances by the pastor reignited the affair.