UFC heavyweight champion Brock Lesnar has withdrawn from his upcoming title defense against Shane Carwin due to illness, UFC President Dana White told Yahoo Sports on Monday.

“He said he’s never been this sick in his life,” White said of Lesnar. “He said it’s been going on for a long time and he just hasn’t been able to shake it.”

Lesnar was scheduled to face Carwin Nov. 21 in Las Vegas at UFC 106. White told Yahoo, however, that Lesnar has been sick for more than three and a half weeks and has been unable to train. White does not think Lesnar has the H1N1 virus, according to Yahoo’s report.

Sherdog.com has not been able to reach Carwin for comment, but he posted on his Twitter account that he was "very disappointed."

"It's (disappointing) hearing about your career and life through the media," Carwin wrote in a second message. "Nothing from the (bosses) yet."

In a third message, Carwin indicated that he had spoken with his manager, Jason Genet, and suggested that the matchup has been postponed until Jan. 2. UFC 108 is scheduled for that date at the MGM Grand Garden Arena in Las Vegas.

UFC.com reported Monday that a light heavyweight matchup between Tito Ortiz and Forrest Griffin will now headline UFC 106.

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» Rossen's Thoughts on Lesnar Dropping Out
» Velasquez, Trainer Break Down Lesnar-Carwin

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This article was updated at 4:55 p.m. EST with information from Carwin's Twitter account and at 5:32 p.m. EST with news that Griffin-Ortiz will headline.