UPDATE: Fight has since fallen through. The bout was set to go down but one or both of the parties could not agree on terms.
Sources close to the bout informed Heavy.com of the news on Thursday morning.
Romero, 32, is a longtime Ring of Combat veteran and has victories over James McSweeney, Karn Grigoryan and Constantinos Phillippou. His last fight took place in November 2009, where he defeated Silmar Rodrigo by submission in the first round.
Cantwell was the final WEC light heavyweight champion before the division was dissolved and all fighters were moved to the UFC division. He last fought in September, losing a unanimous decision in his third and final bout with Brian Stann. Cantwell was scheduled to face Vladimir Matyushenko at UFC 105, but pulled out of the bout due to undisclosed reasons.