updated 03/14/2011 AT 2:00 PM ET
•originally published 03/14/2011 AT 2:40 PM ET
Two days after the former couple drove together to a Hollywood In-N-Out Burger, Wentz, 31, called into Ryan Seacrest’s KIIS-FM morning show to discuss his new band, Black Cards, and to praise Simpson, 26.
“It’s like Ashlee’s been my best friend for five years,” Wentz said Monday. “She’s the mother of my child. I have nothing but love and respect for her. Going through something like this isn’t easy, but we’re friends, and the most important thing is to put our son first.”