U.S. Secretary of State Hillary Rodham Clinton said on Wednesday that she does not want to serve a second term or run for president.

In an interview with CNN's Wolf Blitzer in Cairo during her visit to post-turmoil Egypt, Clinton said "no" to a second term as secretary of state if President Barack Obama is reelected in 2012.

The top U.S. diplomat also said no to serving as U.S. secretary of defense or vice president or president.

"Because I have the best job I could ever have," Clinton explained, saying "this is a moment in history where it is almost hard to catch your breath."

"There are both the tragedies and disasters that we have seen from Haiti to Japan and there are the extraordinary opportunities and challenges that we see right here in Egypt and in the rest of the region," she commented on some major events she has witnessed since taking office in January 2009.

She had visited Haiti several times after a devastating earthquake hit the Caribbean island nation in January 2010, and she will visit Tunisia right after Egypt, where the two countries' long-term presidents stepped down following anti-government demonstrations. Now Japan is suffering from a powerful earthquake as well as ensuing tsunami and nuclear disasters.

"So I want to be part of helping to represent the United States at this critical moment in time, to do everything I can in support of the president and our government and the people of our country to stand for our values and our ideals, to stand up for our security, which has to remain first and foremost in my mind and to advance America's interests," Clinton said.

She added: "And there isn't anything that I can imagine doing after this that would be as demanding, as challenging or rewarding. "

After serving as U.S. first lady for eight years and senator for New York State for about seven years, Clinton launched a presidential nomination bid in 2008 against Obama but lost.

"You know, I had a wonderful experience running and I am very proud of the support I had and very grateful for the opportunity, but I'm going to be, you know, moving on," Clinton said, explaining her refusal to run for president again.

When told that a lot of folks on Twitter had asked if she would run in 2016 for the presidency, Clinton replied: "Well that's very kind, but I am doing what I want to do right now and I have no intention or any idea even of running again. I'm going to do the best I can at this job for the next two years."