The president of the World Boxing Association says Sugar Ray Leonard and Thomas Hearns both may lose their welterweight titles if they go ahead with their planned Sept. 16 fight without approval of the WBA or its rival, the World Boxing Council.

But Mike Trainer, Leonard's lawyer, said the fight will go on as scheduled, although he hopes both organizations will sanction it.

United Press International quoted WBA President Rodrigo Sanchez in Panama City yesterday as saying he had discussed the fight with WBC President Jose Sulaiman and that the two have agreed to have their lawyers study the legalities of the fight.

Sanchez said the two organizations have the power to strip the fighters of their titles if they are found to be in violation of the rules of the sanctioning bodies. Leonard holds the WBC welterweight title and Hearns has the WBA crown.

But Trainer said it was his understanding that sanctions eventually would be forthcoming. "We will request sanctioning. We hope it comes. But the fight will go on anyway," he said.

Concerning reports that it would cost as much as $500,000 to obtain sanctions for the fight, Trainer said he would discuss that with the two organizations.

Sanchez also said that Leonard, who also holds the WBA's junior middleweight title as a result of his June 25 victory over Ayub Kalule, is required to defend that title against Japan's Tadashi Mihara in September.

"That's the first I've heard of it," said Trainer. "Nobody's ever contacted me about it."