WASHINGTON: Democrat Hillary Clinton, seeking to dampen Republican presidential candidate Donald Trump's growing appeal with working-class voters, on Tuesday accused him of having cheered on the 2008 housing market crash.

Clinton's campaign released an ad with audio that the presumptive Republican nominee recorded in 2006 for his now-defunct Trump University venture. Trump, a billionaire real estate developer, in remarks on a "bubble burst," said: "I sort of hope that happens because then people like me would go in and buy" property and "make a lot of money."

Clinton's campaign and her surrogates have seized on the recording to argue that she would take better care of the US economy. Clinton is seeking to blunt the inroads that Trump has been making with voters in crucial states such as Florida and Ohio.

Trump, in a statement released Tuesday afternoon, defended the comments as the mark of shrewd dealmaking, saying he would bring that sort of sharp business acumen to the White House.

"Frankly, this is the kind of thinking our country needs, understanding how to get a good result out of a very bad and sad situation. Politicians have no idea how to do this – they don’t have a clue," he said.

Trump has never held elected office and often touts his history as a businessman in response to accusations that he is unprepared to assume the presidency.

Opinion polls in key states show Clinton, the front-runner for the Democratic nomination, and Trump in a tight race ahead of the Nov. 8 US presidential election. Nationally, Trump has been rising in polls to pull roughly even with Clinton.

US Senator Elizabeth Warren, a Democrat who is a favourite of financial reformers, bashed Trump in prepared remarks released ahead of a speech in Washington on Tuesday. Trump's 2006 comments, she said, amounted to rooting for "people to get thrown out on the street."

"The rest of us were horrified by the 2008 financial crisis," Warren said in the comments. "But Donald Trump was drooling over the idea of a housing meltdown – because it meant he could buy up a bunch more property on the cheap."

Warren also criticized Trump for saying in a Reuters interview last week that the 2010 Dodd-Frank financial oversight law, enacted in response to the crisis, made it hard for bankers to operate.

"Let me find the world's smallest violin to play a sad, sad song," Warren said. "Can Donald Trump even name three things that Dodd-Frank does? Seriously, someone ask him."

Clinton surrogates from Ohio and Florida held a conference call with reporters about Trump's housing statements. Her campaign hosted related events in Virginia, Pennsylvania, New Hampshire, Iowa, Colorado and Nevada, which will all be battlegrounds in November's general election.

"How could Trump possibly champion the collapse of the housing market and our economy?" US Representative Tim Ryan of Ohio said on the call.

Clinton is still fighting on two fronts as she seeks to wrap up her primary battle with Democratic rival Bernie Sanders, a U.S. senator from Vermont.

Clinton and Sanders both campaigned on Tuesday in California, which is among six states holding Democratic nominating contests on June 7. California, the most populous US state, has more Democratic delegates than any other state, and Sanders has invested heavily there.

Clinton needs a solid win in California for a strong finish heading into her party's national convention in July and to dispel questions about whether she can unite the party after a drawn-out, increasingly bitter primary race.

Clinton on Monday turned down an invitation by Fox News to debate Sanders in California despite having agreed previously to a May debate. Her campaign said Clinton's time would be better spent meeting directly with California voters. Sanders said her refusal was an insult to California voters.

Sanders on Tuesday requested that the state of Kentucky review his loss there last week to Clinton by fewer than 2,000 votes. Kentucky's secretary of state, Alison Grimes, said in a statement that the state will recanvas the results at all 120 county boards of election.