(Recasts to add context on decision, comments from justices, analysts, share performance throughout)
By Guillermo Parra-Bernal and Luciana Otoni
SAO PAULO/BRASILIA, May 28 (Reuters) - Brazil's Federal Supreme Court on Wednesday indefinitely delayed a ruling on a landmark savings case dating back more than two decades, handing a temporary victory to the nation's largest banks and the government, and a corresponding defeat to savers who claim they are owed money by the banks.
Brasilia-based STF, as the court is commonly known, made the unanimous decision at a hearing. The decision was taken after a short period of deliberation, in which some justices argued that the court was grappling with a heavy case load.
The savings-account case highlights the legal uncertainties that abound in Brazil, where tax and regulatory disputes with the government can force companies into years of costly litigation. Millions of depositors claim they were incorrectly remunerated when the Brazilian government changed the indexes to which savings rates were pegged between 1989 and 1991.
Savers brought thousands of lawsuits against banks years later. The government argues that a ruling against banks could have devastating consequences on the economy.
A recent study by consultancy firm LCA on behalf of Brazil's central bank estimates a victory for depositors could cost banks between 61 billion reais and 346 billion reais ($27 billion and $155 billion).
Banking shares and bonds led gains, on signs that the court is conscious that a negative ruling could badly affect the nation's banks. With three justices already having recused themselves from the case, investors are hopeful that the remaining court members will swing the case in banks' favor.
Banco do Brasil, which analysts point to as the most affected in a decision against banks, led gains and added 4 percent in mid-afternoon trading. Private sector peer Itaú Unibanco Holding SA rose 2 percent, Banco Bradesco SA gained 1.7 percent and Banco Santander Brasil SA added 1.3 percent.
The yield on Banco do Brasil's 6.250 percent perpetual bond dropped 0.23 percentage point on Wednesday to 7.41 percent. A decline in yields, which move inversely to prices, indicates a decreasing risk perception among investors.
If the STF also rules in favor of depositors, it could hurt President Dilma Rousseff's efforts to revive Brazil's sagging economy ahead of presidential elections in October. State-run lenders would suffer the most and might be forced to turn to the government for fresh capital, analysts said.
An unfavorable ruling could trigger a rating review of the nation's largest banks, depending on the extent of the decision and the financial strength of each bank, credit ratings company Fitch Ratings said last week.
"More moderate members of the court appear to be sensitive to the government's argument that a negative ruling could have a very negative impact on the country's financial sector," said Christopher Garman, director of emerging markets and Latin America policy risk analysis at Eurasia Group in New York.
$1 = 2.24 Brazilian reais Additional reporting by Alberto Alerigi Jr; Editing by Chris Reese