Miley Cyrus Breaks Down During 'Wrecking Ball'

Miley Cyrus broke into tears tonight as she performed "Wrecking Ball" live tonight for the first time, during her show at at the iHeartRadio music festival in Las Vegas.

She started crying during the performance and went offstage to hug her mom.

The song, with lyrics that would lead one to believe she is singing about former boyfriend Liam Hemsworth, is her first No. 1 hit on the Billboard Hot 100.

The two recently broke off their engagement, their reps confirmed to ABC News last week.

(Credit: Al Powers/Powers Imagery/Invision/AP)

Cyrus, 20, and Hemsworth, 23, first met in 2009 on the set of their movie "The Last Song" and were engaged in 2012. However, by the spring of 2012, rumors had begun circulating that the relationship was on the rocks.

See Miley Cyrus Naked in Her 'Wrecking Ball' Video

The "We Can't Stop" singer shot them down though, showing off her engagement ring on "Good Morning America" in June, and said in the ABC News Celeb Quiz that she hoped to go to the moon with "my honey."