OMAHA, Neb. - With billionaire investor Warren Buffett looking on, Democratic presidential candidate Hillary Clinton said Wednesday she wants to raise taxes on the wealthy and expand upon the so-called "Buffett rule" pushed by the Obama administration to raise tax rates on the richest Americans.

"I want to go even further, because Warren is 100 percent right, as usual," Clinton said at a rally in Omaha that featured a public endorsement from Buffett, the famed investor and one of the wealthiest people in America. "I want to be the president for the struggling, the striving and the successful."

Introducing Clinton, Buffett offered a litany of statistics describing a growing chasm between the nation's rich and poor, lamenting that "millions and millions and millions of Americans have been left behind." Buffett was the namesake for the push by the Obama administration to seek a tax rate of 30 percent on those earning $1 million or more.

The so-called "Oracle of Omaha," said he would be "delighted" if Clinton takes the oath of office, asserting that she will not forget about middle-class Americans.

In her primary campaign against Vermont Sen. Bernie Sanders, Clinton has pushed back against concerns among some liberals that her time in the Senate representing New York left her too close to Wall Street bankers - a notion that Buffett's appearance was aimed at allaying.

Republicans sought to brand her as a tax-and-spend liberal, unsympathetic to the economic pains of everyday American families.

"Hillary Clinton's economic agenda is more about redistribution than growth," said Republican National committee spokesman Michael Short, in a statement. "Campaigning with the third richest person on the planet is an odd way to communicate that she understands and cares about the needs of millions of Americans."