BJ Penn knows there are bigger fights for him in the future.

For now, he is calling tomorrow's world championship bout against Frankie Edgar his biggest.

"If you slack off on a guy like Frankie Edgar, then you're not a real champion," Penn said. "One of the hardest things to do in fighting is to win when you're supposed to win."

And Penn is expected to win tomorrow.

He will defend his UFC lightweight world championship against Edgar in the co-main event of the "UFC 112: Invincible" mixed martial arts card. The event is being staged at Yas Island, Abu Dhabi, United Arab Emirates.

Penn, who is from Hilo, has a professional record of 15-5-1, including 5-0 in his last five UFC lightweight bouts.

Edgar, who is from Toms River, N.J., is 11-1.

The bout — which is scheduled for five 5-minute rounds — should become a battle of wills.

Edgar, who has a solid wrestling background, is known for his aggressive takedowns. He is averaging four successful takedowns per bout.

Penn, a former jiu-jitsu world champion, is known for his takedown defense. No lightweight (155 pounds) fighter has been able to score a successful takedown of Penn in six years.

But Penn has also become one of the sport's most feared strikers. In his last title defense in December, Penn turned challenger Diego Sanchez's face into a bloody mess with an onslaught of kicks and punches, prompting a stoppage in the fifth round.

"If I'm going to win the belt, I want to win it from the best guy there is, and that's BJ Penn, hands down," Edgar said. "There's no single game plan or blueprint to beat BJ. I think you're going to have to kind of almost draw that blueprint in those 25 minutes."

Online gambling sites are listing Penn as a -800 favorite, which basically means that a bettor would have to risk $800 on Penn to win $100.

"I've said many times, you know, Frankie Edgar is not the guy to look past," Penn said. "Anybody who looks past Frankie Edgar is going to end up with another loss on their record, and you know, this isn't a guy you play around with. So I'm not thinking anything past (tomorrow)."

At the same time, Penn acknowledged that a victory could prompt him to move up to the welterweight (170 pounds) division.

"Yes, if everything goes well (tomorrow), I definitely would consider moving up to 170," Penn said. "Not that it's 100 percent guaranteed. There's still a lot of good contenders in the 155-pound division, but I'm thinking about (moving up)."

Penn was the UFC welterweight world champion in 2004. He is one of just two fighters who have won UFC world titles in two separate weight classes (Randy Couture is the other).

However, Penn is 0-3 in his last three welterweight bouts.

"If I do make that move (to welterweight), I'm going to move slow," Penn said. "I'm not going to rush anything."

UFC president Dana White has stated that he would prefer Penn "clean out" the lightweight division before moving up to welterweight.

Penn said there still are worthy contenders in the lightweight division. In particular, Kenny Florian is posturing for a rematch with Penn, and Gray Maynard is 9-0 as a lightweight.

"I honestly believe that you can never really clean out a weight class because there's always going to be a new contender," Penn said.

Penn opted to train in Hilo for this bout because of the expected warm weather in Abu Dhabi. Throughout most of 2009, Penn's training camps were in Southern California.

Tomorrow's card will be staged in an outdoor arena.

In an effort to acclimate to the conditions, Penn has been in Abu Dhabi since March 25.

"When I first got here it was tough, actually," Penn said. "But it's similar weather to Hilo right now with the humidity, and I think we're right on schedule."

GROVE ON UNDERCARD

Maui's Kendall Grove will face California's Mark Munoz in a middleweight (185 pounds) bout on tomorrow's undercard.

Grove is 13-6, including 3-1 in his last four UFC bouts. Munoz is 7-1.

"I expect the unexpected," Grove said. "He's a great wrestler, but you never know. He might come out striking."

Grove, who is 6 feet 6, will have a 6-inch height advantage.

"(Grove) poses a lot of problems just because of his height, and just how good he is," Munoz said.