Eddie Alvarez has long considered himself the best lightweight in mixed martial arts. He gets to prove it Sept. 17 against Donald Cerrone at UFC 178 in Las Vegas.

On Tuesday, Alvarez and Bellator MMA announced that they have parted ways. The agreement allowed Alvarez, the reigning Bellator 155-pound titleholder to become an unrestricted free agent - opening the door for him to finally sign with UFC.

Alvarez wasted no time joining the highest-profile MMA promotion. The parties reached a contractual agreement Tuesday night. And Alvarez immediately signed to face Cerrone at MGM Grand Garden Arena.

"This is going to be an extremely fan friendly fight," Alvarez said, according to Yahoo! Sports.. "How can it not be? You have two guys with the some of the highest finish ratios in all of the sport. You know people are going to love this fight. How can they not?

"These kinds of fights, these big fights that get everyone talking and interested, these are the fights I want. I want to fight only dangerous guys. Whenever I've done that in my career, I've stepped up and risen to the challenge."

The 30-year-old Alvarez will carry a professional record of 25-3 into his UFC debut. Cerrone [24-6, 1 no contest] is on a four-fight win streak.