SAN FRANCISCO -- Hillary Rodham Clinton on Saturday forcefully challenged the nation to confront persistent racism in the wake of the mass shooting in Charleston, S.C., declaring that "race remains a deep fault line in America."

"Despite our best efforts and our highest hopes, America’s long struggle with race is far from finished," Clinton told the U.S. Conference of Mayors at its annual convention here. "I know this is a difficult topic to talk about. I know that so many of us hoped by electing our first black president, we had turned the page on this chapter in our history. I know there are truths we do not like to say out loud or discus with our children. But we have to."

Clinton's appearance here came three days after nine people were shot to death at the Emanuel African Methodist Episcopal Church. Dylann Roof, 21, has been charged with murder in the case.

Although Clinton had called for stronger gun curbs during an appearance in Las Vegas on Thursday, her remarks in San Francisco marked a far more forceful foray into race relations, which have been strained in several cities amid a series of racially charged protests over the deaths of African Americans at the hands of police officers.

Obama addressed the mayors on Friday, and he also spoke about the Charleston shootings, while calling for stricter gun laws. The president has anguished over Congress's failure to approve his 2013 push for tighter controls, including more background checks and limits to ammunition magazines, in the wake of the massacre of more than two dozen students in Newton, Conn., in Dec. 2012.

Clinton vowed to complete what Obama was unable to in Congress. "The president is right: The politics of this issue have been poisoned, but we can’t give up," she said. "The stakes are too high; the costs are too dear. I will not be afraid to keep fighting for common sense reform and with you achieve that for all who have been lost because of senseless gun violence."

Obama has spoken more pointedly about race in his second term. Clinton's foray into the nation's legacy of racism came as she has sought to inspire early enthusiasm among the liberal base of the Democratic Party, staking out progressive positions on immigration, gay marriage and trade. Clinton advisers are hoping to recreate much of Obama's coalition of black, Hispanic and female voters to help push her candidacy in a 2016 battle against a Republican nominee.

Gun control could become an issue in the 2016 campaign; so could race relations, and Clinton made clear she would not shy away from talking about the subject. She said the problem of racism was not limited to "kooks and Klansmen," but also was perpetrated by the off-hand joke, by whites not wanting to live near blacks and by those affluent whites who are fearful of young black men.

"Let's be honest," she said.

Clinton also praised the families of the Charleston victims, including those who told Roof that they would forgive him, when he appeared in his first court proceedings.

"Their act of mercy is more stunning than his act of cruelty," she said. Wrapping up, she added that "what we need more of in this country is love and kindness."

Clinton's visit to this city was the last stop on a week-long national tour after her official campaign launch last weekend in New York.

She raised money Friday at a pair of fundraisers in Los Angeles, including one at the home of actor Tobey Maguire.

Obama also raised money for fellow Democrats in the 2016 election cycle during his California trip, attending two events in Los Angeles and two more in San Francisco. The president was scheduled to travel to Palm Springs on Saturday to play golf before returning to Washington on Sunday.