Ashlee Simpson, 23 and her rocker boyfriend, Pete Wentz, 28, are tying the knot, Usmagazine.com has confirmed.

A rep for Simpson tells Us, "Yes, they are happily engaged."

Earlier today, the singer told Us, "I'm really happy!"

One possible cause for the quickie engagement - a pregnancy, to which her rep had no comment and referred Us to friendsorenemies.com, where Simpson posted the following Wednesday:

"We know there has been a lot of speculation recently about Pete and I, and we wanted our fans to be the first to know, because you guys are the best. Yes, we are thrilled to share that we are happily engaged."

Simpson and Wentz began dating in late 2006. (See what a body language expert had to say about their relationship here.)

"They are ecstatic and can't wait to be man and wife," a source tells Usmagazine.com "They will be getting married before the end of the year."

Wentz told Us this month that he was open to marriage.


"When you find someone you think is your soulmate, it's inevitable," he said.

[ Read more celebrity news at Usmagazine.com ]