The 26-year-old singer recently spoke to Entertainment Tonight and told host Rob Marciano he "absolutely" still loves Duff. The two dated from 2001-2003 before the relationship ended amid rumors that Carter had cheated with Lindsay Lohan.
"I don't know who she is today," the singer admits in the interview. "She doesn't know who I am today, but I would sweep her off her feet if I ever got a chance to again and fix what I did wrong."
The open adoration is not Carter's only recent declaration of love. The star had taken to Twitter in March to confess his lingering feelings for his ex.
"I'll spend the rest of my life trying to better myself to get back to her," he wrote. "Don't be that stupid douche that loses the love of your life forever.. Like me."
Carter says now that the tweets weren't "meant for the media or anybody like that." The singer says he "didn't think about it really," and "wasn't really looking for [a response] either."
"I'm sure she got the message," he says. "I'm going to do everything in my power...to fix the relationship I had with the love in my life. I'm not gonna give up on Hilary... ever."
Duff separated from husband Mike Comrie in January. The couple have one child together, son Luca Cruz Comrie.
Celebrity Families of 2014 [PHOTOS]