Hugh Hefner and Crystal Harris
06/14/2011 at 06:00 PM EDT
They rang in the holidays with news of their engagement
, but there will be no wedding bells after all for Hugh Hefner and Crystal Harris.
The playmate, 25, called off the nuptials on Tuesday, just days before they were to tie the knot
Saturday at the Playboy Mansion.
"The wedding is off," Hefner Tweeted
. "Crystal has had a change of heart."
"After much deep reflection and thought I have decided to end my engagement with Hef," Harris wrote
on her website. "I have the utmost respect for Hef and wish him the best going forward. I hope the media will give each of us the privacy we deserve during this time."
More than 300 people had been invited – via Papeterie custom-made invitations – to their big day
, which called for a pink Romona Keveza gown and Torrance Bakery strawberry cake.
This would have been the third marriage for Hefner, 85, who filed for divorce
in 2009 from his second wife, former playmate Kimberly Conrad. He was previously married to Mildred Williams, whom he divorced in 1959.
"I heard the sad news today this morning," Harris's manager Michael Blakey tells PEOPLE. "The split was a mutual decision and the two remain good friends."
The wedding cancellation was first reported by TMZ