Demi Lovato Meets President Obama At Christmas In Washington Concert

Demi Lovato met the president of the United States on Sunday and couldn't hold back her excitement.

The 20-year-old singer was present at the Christmas in Washington concert event at the National Building Museum. The former Disney star and current judge on the "X Factor" got the chance to meet President Barack Obama and First Lady Michelle Obama while mingling with other guests after her performance.

"OH MY GOD.. I just met the PRESIDENT OF THE UNITED STATES!!!!! Our First Lady is GORGE. So excited right now!!!" Lovato tweeted after the encounter.

Shortly after her first tweet, she composed herself for a slightly more demure message: "Such an honor singing for the President and the First Family."

Lovato and a handful of other stars were present at the event hosted by Conan O'Brien, which will be broadcasted on TNT. The lineup of performers included Diana Ross, "American Idol's" Scotty McCreery and Chris Mann.

Another singer present was PSY, who gave a performance of his hit "Gangnam Style" in holiday attire that included Christmas red outfits and reindeer antlers. The appearance of the South Korean pop star came two days after he apologized for the controversy created when it was discovered that he participated in anti-American concerts in his home country years back.

"The specific words that I used, it was too much. If it's gonna hurt my career or not, that's not important," PSY said to Rolling Stones backstage at Sunday's event about his past lyrics, which included derogatory remarks toward the U.S. "The most important thing is that as a human being, I really, fully regret the using of [those] kinds of words."

The 31st annual Christmas in Washington benefit concert will air on TNT on Dec. 21, 2012. Proceeds of the event support the Children's National Medical Center.