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UFC heavyweight champion Brock Lesnar has withdrawn from his upcoming title defense against Shane Carwin due to illness, UFC president Dana White told Yahoo!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

"[Lesnar] said he's never been this sick in his life," White said, according to Yahoo!. "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.

Carwin posted on his Twitter account that he was "very disappointed." Sherdog.com has been unable to reach Carwin.

Later, he wrote "...Looks like it is posponed till [Jan.] 2. I had [the H1N1 flu virus] myself and I understand how devastaing it can be."

White told Yahoo! he doesn't think Lesner has H1N1.

UFC 108 is scheduled for that date at the MGM Grand Garden Arena in Las Vegas.

"It's [disappointing] hearing about your career and life through the media," Carwin wrote in another message.

Information from Sherdog.com is included in this report

Lesnar sick, withdraws from bout