CHICAGO -- UFC heavyweight champion Cain Velasquez said Thursday that boxing contender Tyson Fury, who publicly challenged him to a fight "in a cage or ring," will have to do more than tweet challenges and insults to get his wish.

Cain Velasquez said if Tyson Fury wants to fight him, he'll have to earn the right. Josh Hedges/Getty Images

Fury (20-0), who stands 6-9 and is ranked No. 10 in the world by The Ring magazine, apparently has grown frustrated that he hasn't been able to secure a championship bout in the ring against one of the Klitschkos, so Fury challenged the 6-1 Velasquez.

"I didn't know who he was until this," Velasquez told ESPNChicago.com. "I think he's using my name to gain publicity, which he has done, everybody is bringing it up."

Fury issued the challenge via Twitter.

"I challenge u to fight all in in a cage or ring! It could be billed as the man vs midget lets get it on!" Fury tweeted.

Velasquez smirked a bit when reminded of the insult, but he wasn't taking the bait.

"I'm not a boxer," he said. "I'm a mixed martial artist, and if he wants to fight, he can go into the UFC and work his way up like everybody else does. Nothing is given to you in this world.

"To me, it's like don't talk about it, go ahead and do it. That's all I have to say about that."

There have been cross-sports fights, including Ray Mercer knocking out former UFC champ Tim Slyvia and Randy Couture beating James Toney. Velasquez was asked if he would be interested in such an event if his title weren't on the line.

"You have to work your way up the ladder, just like everybody else," he said. "Nothing is given to you in this world, so you have to work hard."

Velasquez was in town to promote UFC on Fox 6 on Jan. 26 at the United Center.

ESPN Chicago's Ray Flores contributed to this report.