Kelly Osbourne has bailed on her much-anticipated Tonight Show appearance this Friday saying she'd broken her hand and was exhausted.

"Kelly has been doing a lot of traveling the last few weeks and is absolutely exhausted," said Lisa Vega, Osbourne's publicist, by way of explanation. 

"Plus, she broke her hand falling down some stairs." 

Some people close to the TV family earlier said that the young Osbourne daughter canceled on the Tonight Show because she had to travel to England for MTV to publicize The Osbournes over there. 

"There had been some talk [of her going to England] but nothing was absolutely confirmed," Vega said. 

Osbourne was booked to sing her new single — a remake of Madonna's "Papa Don't Preach"  on Friday's Tonight Show as part of its "Lincoln Garage Concert" series. 

Kelly performed "Papa Don't Preach"  to mixed reviews on MTV's movie awards show last week and has made video version of the song that has yet to air. 

The Tonight Show said in a press release that Osbourne "had a scheduling conflict." A show spokeswoman said Osbourne's appearance will be rescheduled for a later date. 

Kelly Osbourne, her brother Jack and parents Sharon and Ozzy have previously appeared on the Tonight Show

During one of Ozzy and Sharon's visits last month, Ozzy uttered the f-word  which the show failed to bleep. 

Kelly Osbourne will be replaced this Friday by crooner Chris Isaak, who recently traveled abroad with Tonight Show host Jay Leno.