'American Idol' duo end romance

American Idol's David Cook and Kimberly Caldwell have ended their relationship.

The pair split just before Christmas, according to Us magazine.

"They didn't want to make a big deal about it." said a source. "[David] has a lot of options and wants to explore them. He doesn't want to be tied down."

The source also claimed that reports Cook proposed to Caldwell with a Tiffany diamond were not accurate.

"That rumour was not true," they said. "The relationship just sort of dissolved."

Cook started dating the American Idol season 2 contestant in May 2008 after he asked her out during a red carpet interview.