Cycling star Lance Armstrong blames Sheryl Crow's biological clock for their relationship breakdown.

Armstrong and singer Crow dated for three years and were engaged to be married, but split in February 2006. Armstrong has three children from his previous marriage to Kristin Richards, but insists he wasn't ready for kids with Crow as he was still recovering from his divorce.

And in his upcoming tell-all book Lance, he admits the pressure of Crow's advancing years finally broke them apart, according to New York gossip column PageSix.

He writes, "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 gotten out of a marriage, I'd just had kids. Yet we're up against her biological clock - that pressure is what cracked it. Because if somebody wants a child - man, that's the greatest gift you can give to a woman - so who are you to stand there and say I don't want one. So we were at different points in our lives. We were not compatible on that issue."

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(This news article provided by World Entertainment News Network)