Sen. Marco Rubio, a potential 2016 presidential candidate, says he never claimed that Hillary Clinton, another potential candidate, is too old to run for the position.

In an interview with NPR's Morning Edition Show on July 22, Rubio, a Florida Republican, shared his opinion on Clinton's chances in the 2016 campaign.

"I just think she's a 20th century candidate," he said. "I think she does not offer an agenda for moving America forward in the 21st century, at least not up till now. ... The truth of the matter is she was the secretary of state during an administration that has had virtually no successes on foreign policy."

The Senator added that Clinton is on the wrong side of the country's "generational, transformational crossroads."

Some thought Rubio was suggesting that Clinton, 66, is too aged to be the next president, but on Sunday, Rubio, 43, denied this.

"You can be 40 years old and be a 20th century candidate," Rubio said on "Fox News Sunday," according to Fox News Latino.

Rubio reiterated, however, that Clinton is behind the times.

"We are going through the equivalent of an industrial revolution every five years, and I don't think she or her party, and quite frankly, even some people in my party, have answers to that," he said,

This is not the first time age has come up in a presidential race. In 1984, President Ronald Regan, 73 years old at the time, briefly discussed age in a debate against Walter Mondale, who was 56 years old.

"I will not make age an issue of this campaign," the late former president said. "I am not going to exploit, for political purposes, my opponent's youth and inexperience."

Neither Marco nor Clinton has officially confirmed that they will run in the 2016 election. Rubio told NPR that he will decide by the beginning of 2015.

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Follow Scharon Harding on Twitter: @ScharHar.

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