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Hillary Clinton Says While "All Doors Open," No Presidential Bid Yet

State Department photo(NEW YORK) -- When Hillary Rodham Clinton steps down from her post as secretary of state as expected early next year, her political career will have spanned over two decades.

She is by far the most popular official in the Obama administration, and is already the leading candidate should she choose to run for president again in 2016. So is this really goodbye for the former first lady, senator and secretary of state? Or will Hillary Clinton, who recently turned 65 years old, re-invent herself once again?

In an exclusive interview with ABC’s Barbara Walters, Clinton said that while "all doors are open" for her future, one thing is for certain: she is definitely leaving the cabinet as soon as a new secretary is sworn in.

"It sounds so simple, but I've been, as you know, at the highest levels of American and now international activities for twenty years, and I just thought it was time to take a step off… maybe do some reading and writing and speaking and teaching," said Clinton.

She told Walters that she doesn't have a plan for what she'll do immediately after leaving political life, but has considered working in philanthropy or academia. When pressed on whether her future includes a widely-speculated 2016 run for president, Clinton maintains that she still does not plan to run.

"I've said I really don't believe that that's something I will do again," she said. "I am so grateful I had the experience of doing it before."

She went on to say, however, that if she did choose to run she would not be concerned about her age. Clinton would be 77 years old at the end of a second term.

"I am, thankfully, knock on wood, not only healthy, but have incredible stamina and energy," she said.

She did admit that being the most-traveled Secretary of State in U.S. history has taken a toll.

"Being on planes, as you know, as much as I am, takes something out of anybody, doesn't matter how old you are, or how often you've done it," she said. Clinton, who has traveled to 112 countries as a member of President Obama’s cabinet, said she replenishes her energy by drinking a lot of water, trying to swim and do yoga when time permits and regulate her sleep.

Her darkest moment as Secretary of State happened this year when terrorists in Libya attacked the U.S. consulate in Benghazi on September 11th, killing four Americans, including U.S. Ambassador Chris Stevens. Clinton calls the attack the "worst time" in her tenure.

"It's something that is certainly terrible," she said. "We take risks in the work we do. The people who do this work, are often in very threatening environments, whether it's our military or our civilian people around the world, I have just the most extraordinary admiration for them."

Clinton, who knew Stevens personally, has repeatedly said that no one wants to find out what happened in Benghazi more than she does. The results from an internal State Department investigation are expected to be released soon.

Clinton said she is leaving the office feeling immensely proud of what has been accomplished over the last four years.

"When I became secretary, when the president took office, we were in the midst of a terrible economic downturn, but we also were experiencing some very negative attitudes toward our country,” she said. "I don't think there's any doubt now, and we have gone through enormous difficult changes, but I think everyone knows that the United States and our leadership is to be counted on."

Copyright 2012 ABC News Radio

ABC News Radio