SAO PAULO, Sept 10 (Reuters) - Brazilian telecom Grupo Oi SA reiterated on Wednesday it had commissioned investment bank BTG Pactual to seek possible partners in a joint bid for rival wireless carrier TIM Participações SA.

Oi neither confirmed nor denied reports that BTG is reaching out to Spain's Telefonica SA and Mexico's America Movil SAB de CV in a deal that would break up the local unit of Telecom Italia SpA.

"BTG Pactual's role is to make contact with any entity that could participate in the operation, even in light of potential regulatory and competitive restrictions that could result," Oi said in a regulatory filing.

"(Oi) is still not involved, at this point, in any formal negotiations with any third parties on this subject," the company added.

Carlos Slim's America Movil confirmed on Monday that it plans to hold talks with Oi to make a joint bid for TIM. Telefonica has declined to comment on the rumors, which gained steam since late last year.

Breaking up TIM would give rivals more breathing room in Brazil's crowded four-way mobile market, where they have struggled to add customers, invest in high-speed networks and protect profits in a stagnant economy.

(Reporting by Brad Haynes; Editing by Cynthia Osterman)