(Adds CSN comment)
SAO PAULO, June 16 (Reuters) - An appeals judge in Brazil has overturned a ruling by the country's antitrust authority that allowed steelmaker CSN to make appointments to the board of rival Usiminas, in which it has a stake.
The ruling by Judge Jirair Aram Meguerian on Wednesday could mean CSN's two appointees will have to step down from the Usiminas board, which grew to 11 members after the regulator, known as Cade, cleared the way for the move in April.
The ruling was announced on the court's website.
CSN, formally known as Companhia Siderúrgica Nacional SA, said in a statement it was surprised by the decision, adding that the board members it appointed were crucial to the running of Usiminas.
"CSN will spare no effort to ensure the presence of independent board members on the board of Usiminas, because of the belief that they are crucial for the company to get back on track and return to growth," the statement said.
The case, one of several connected to Cade's decision, is another chapter in an ongoing shareholder battle for control of the Usiminas boardroom.
Controlling shareholders, Nippon Steel & Sumitomo Metal Corp and Techint, have been at loggerheads for nearly two years, while CSN, which owns a significant stake but is outside the controlling group, is exerting increasing influence.
CSN, formally known as Companhia Siderúrgica Nacional SA, owns 19 percent of Usiminas preferred shares and 10 percent of its common shares, according to Thomson Reuters data. (Reporting by Alberto Alerigi; editing by Paul Simao and Richard Chang)