Cycling great Lance Armstrong has opened up about his split from musician Sheryl Crow.

The Tour de France legend says he and the singer broke-up three years ago because of her biological clock.

Armstrong says in a new book that after the couple got engaged, in 2005, their relationship became “kind of a struggle”.

“She wanted marriage, she wanted children; and not that I didn’t want that, but I didn’t want that at that time because I had just [come] out of a marriage, I’d just had kids,” Armstrong tells author John Wilcockson in his biography, Lance.

Armstrong, 37, says he and Crow went to a relationship counsellor, but could not fix the situation.

“We were at different points in out lives. We were not compatible on that issue,” Lance reveals.

"I felt like I wasn’t ready. I would have been in the future, but not then.”

Crow eventually adopted a baby boy in May 2007, who she named Wyatt Steven Crow.

Armstrong, already a father of three, is set to be a dad again as his girlfriend Anna Hansen is currently pregnant.