Campbell linked up with Betis last summer and has scored two goals in La Liga this season after spending last term on loan in France with Lorient.
The Costa Rican joined Arsenal in 2011 from Deportivo Saprissa, but has yet to receive a work permit to play in England and recently said he is enjoying his time with Betis.
Now Mel is hoping to keep the 20-year-old for another year and talks are scheduled to take place with Arsenal early next month.
"We are advancing the negotiations to reach an agreement," Mel told Estadio Deportivo.
"This won't be easy, but we want to speak in London with clarity and to agree a new loan. I believe that it will be positive for all parties."