Hillary Clinton: make the rich pay more tax

Instead, Mr Obama favours higher taxes for the nation's wealthiest.

Talking in general terms at the Clinton Global Initiative, Ms Clinton insisted: "There are rich people everywhere and yet they do not contribute to the growth of their own countries.

"They don't invest in public schools, in public hospitals, in other kinds of development internally," she told the aid foundation set up by her husband, former Democratic president Bill Clinton.

But as countries seek to stop being aid recipients, Ms Clinton said taxes were vital to "mobilize their own domestic resources for long-term development".

"And so it means for leaders telling powerful people things they don't want to hear," said Ms Clinton.

"It means being transparent about budgets and revenues, and bringing corruption to light and when that happens, we shouldn't punish countries for uncovering corruption; we should reward them for doing so.

"And it means putting into place regulations designed to attract and protect investment."

Ms Clinton, who was defeated by Obama in 2008 to be the Democratic presidential candidate, has so far ruled out a run in 2016.

On Sunday, Bill Clinton left the matter open, saying: "I have no earthly idea what she will decide to do."

"I think we ought to give her a chance to organize her life and decide what she wants to do," he added.