SAO PAULO, Brazil (AP) _ Brazil, the world's largest orange juice exporter, will only begin benefitting in June from the recent frost damage to U.S. citrus crops, government and industry spokesmen said Wednesday.

''Practically all of our 1984-85 production has already been sold and we still don't have an exact idea of how much juice we have left over to satisfy any additional demand from the United States,'' Sergio Ribas, press spokesman for Cacex, the government's import-export agency.

''Brazil is not in a hurry to export orange juice and prefers to wait until the exact extent of the frost damage is known,'' he added.

''We will most likely benefit from the frost in June when the harvesting of the 1985-86 crop begins,'' Ribas said.

Hans Georg Krauss, president of the Brazilian Citrus Juice Industry Association, said that during the 1984-85 season some 700,000 tons of orange juice was produced from a crop of about 185 million boxes.

''Of the 700,000 tons of juice, Cacex earmarked 620,000 tons for export between July 1984 and June 1985. But, because of an increase in demand, mainly from the United States, we finished selling the 620,000 tons in December 1984, leaving us with a very small surplus,'' Krauss said.

''Unlike 1983, this year's frost won't bring us any immediate advantages. We will have to wait until our next harvest begins,'' he said.

According to Krauss, the 1985-86 crop is expected to yield about 190 million boxes of oranges - ''enough to produce some 720,000 tons of juice.''

He said he hoped the frost would not lead to a sharp increase in international prices ''because that would only scare away the consumer.''

The minimum export price for Brazilian orange juice is now at $1,800 a ton.

When Florida citrus crops were hit by a frost in 1983, Brazil had a surplus of about 150,000 tons of orange juice which it quickly sold to the U.S.

''Because of that frost, our 1984 exports rose to 911,002 tons worth, $1.425 billion,'' Ribas said.

The previous year, Brazil exported 554,362 tons valued at $609 million.