Former president Jimmy Carter says he would not be able to run for president today because the U.S. political system has warped into an 'oligarchy' which requires huge financial wealth.

In a new interview, the 91-year-old said the need for massive financial backing excluded candidates and warned against the 'damaged' ethical standards of American politics.

During an interview with Oprah for her upcoming episode of SuperSoul Sunday, he was asked if could become president today.

He replied: 'Absolutely not. There's no way now for you to get a Democratic or Republican nomination without being able to raise $200 or $300million or more.

'I would not be inclined to do that, and I would not be capable of doing it.'

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Former president Jimmy Carter says U.S. politics have become an 'oligarchy' rather than democracy

He went on to warn that the need for such massive financial backing had caused irreparable damage to the U.S. political system.

'We've become now an oligarchy instead of a democracy, and I think that's been the worst damage to the basic moral and ethical standards to the American political system that I've ever seen in my life.'

Mr Carter then discussed the modern divide between Democrats and Republicans, which is now much more partisan than it was when he ran for office in 1976.

He said: 'When you get to Washington, you've already alienated Democrats from Republicans, and Congress from the president, and red states and blue states.

'We never had any of that 25 or 30 years ago.

'I had just as much support from Republicans as I did Democrats when I ran for president. But I should have organized the Democratic Party to get me re-elected.'

Carter was the nation's 39th president, advancing as a virtual unknown on the national stage to defeat President Gerald Ford in 1976.

The peanut farmer from rural Georgia rebuilt his career as a humanitarian guiding the center focused on global issues, including health care and democracy.

Carter earned a Nobel Peace Prize in 2002, helped defuse nuclear tensions in the Koreas and helped avert a U.S. invasion of Haiti.