Hayden Panettiere's fiancé thinks she's "the best mom."

Wladimir Klitschko and Hayden Panettiere

Wladimir Klitschko and Hayden Panettiere

Wladimir Klitschko admits his life has changed completely since the 'Nashville' actress, 25, gave birth to their eight-week-old daughter, Kaya, in December and says their baby girl has helped them form a connection "better than any marriage."

Asked about fatherhood, the Ukrainian boxer said: "It changed my life completely. I'm so happy to have Hayden in my life. She's the best mom I could even imagine. She's a true, amazing mom."

The couple, who got engaged in March 2013, have no immediate plans to get married.

The 38-year-old fighter told UsMagazine.com: "Now is for now -- when people get married there are different things they promise to each other and I understand the promising part, but I think [having] children is something that connects you until the end of your days no matter what. And I think that, Kaya, our daughter, has connected us forever. And that's the most amazing thing. Everything else is coming, it's something that needs to be planned...but as I said, the connection with the child is better than any marriage!"

The couple aren't getting a lot of sleep at the moment, but Wladimir claims Kaya's smile gives him "a boost of energy."

He said: "She can communicate with her eyes and smile. Even if you're tired and haven't slept enough, when you look at your child's eyes, [it's like], 'For you, little angel, I'm going to do everything! Literally everything.' I don't know what appreciation she's expressing but it's something like, 'Thank you for being here in my life, Dad, and being around.' It's something that gives you a boost of energy."