Former president Bill Clinton strongly defended foreign donations to his family's charitable foundation and said that no entity gave the foundation money to try to influence his wife, Hillary Rodham Clinton, while she served as secretary of state.

In an interview with NBC News that aired Monday morning, Clinton also said he would continue to deliver six-figure paid speeches during his wife's presidential campaign because, he said, "I gotta pay our bills."

Clinton said that neither his family nor the Bill, Hillary and Chelsea Clinton Foundation have done anything "knowingly inappropriate" by accepting donations from foreign governments.

“There is no doubt in my mind that we have never done anything knowingly inappropriate in terms of taking money to influence any kind of American government policy," Clinton said. "That just hasn't happened."

He said Hillary Clinton has told him, "No one has ever tried to influence me by helping you."

The foundation's finances and practice of accepting donations from foreign governments in particular have drawn considerable scrutiny in recent weeks from The Washington Post and other news organizations and in a new book, "Clinton Cash." With Hillary Clinton beginning her campaign for the 2016 presidential nomination, the foundation has become fodder for attacks from her opponents, both Democratic and Republican.

Bill Clinton said he believed there has been a "very concerted effort to bring the foundation down," arguing that the Clintons are being held to a higher standard than other politicians. "The idea that there's one set of rules for us and another set for everybody else is true," he said.

The Clinton Foundation recently bowed to pressure and announced it would restrict foreign donations to only six Western nations and increase transparency by disclosing its donors four times a year instead of once annually.

Bill Clinton spoke with NBC from Kenya during his and daughter Chelsea's annual tour of Africa to visit Clinton Foundation projects that focus on such issues as climate change, public health, conservation, economic growth and empowering women and girls.

"There has never been anything like the Clinton Global Initiative, where you've raised over $100 billion worth of stuff that helped 43 million people in 180 countries," Clinton said. "I don't think there's anything sinister in trying to get wealthy people in countries that are seriously involved in development to spend their money wisely in a way that helps poor people and lifts them up."

But he left open the possibility that he would step down from the foundation if his wife is elected president.

"I might if I were asked to do something in the public interest that I had an obligation to do," Clinton told NBC. "Or I might take less of an executive role. But we'll cross that bridge when we come to it."

Asked about his paid speeches, some of which come with a fee of $500,000 or higher, Clinton said, "People like to hear me speak."

Clinton said it was "laughable" for people to assume that Hillary Clinton couldn't "relate to the currents of middle class America because now we have money."

"I'm grateful for our success," he said. "But let me remind you: When we moved into the White House, we had the lowest net worth of any family since Harry Truman."

See the NBC News interview: