SAO PAULO, Oct 3 (Reuters) - Petrobras has

inked an agreement to supply steelmaker Ternium ( TX ) with

natural gas in Rio de Janeiro, the Brazilian state-run oil firm

said on Thursday, marking the first commercial deal between the

two South American majors.

The companies also intend to develop other partnerships and

seek synergies in the natural gas market, Petrobras added in a

statement, saying the move would come "in line with the

steelmaking sector's decarbonization agenda."

Petrobras did not disclose the deal's financial details.