Clinton's comments are similar to ones made by President Obama and Vice President Biden, who have repeatedly attacked Mitt Romney and Republicans as proponents of tax cuts for the rich at the behest of the middle class. Obama has repeatedly advocated for extending the Bush-era tax cuts for income up to $250,000 a year and allowing the tax cuts on income above that to expire.

The comments are particularly notable because as Secretary of State, Clinton has worked to stay away from getting into presidential politics. As is customary, she did not appear at the Democratic National Convention in Charlotte, N.C., earlier in the month.

In the same speech Clinton also said it was important for the wealthy to invest more.

"They don't invest in public schools and public hospitals and other kinds of development internally," Clinton said. "So it means for leaders telling powerful people things they don't want to hear. It means being transparent about budgets and revenues and bringing corruption to light."