A spokesman said yesterday that 16,485 tickets have been sold for Sugar Ray Leonard's defense of his World Boxing Council welterweight championship against Roberto Duran June 20 in Montreal's Olympic Stadium.

Giles Bourcier, head of the information center for the Olympic Installation Board, the Montreal promoter, said there will be 77,263 seats available.

Ticket prices are $500, $300, $200, $150, $75, $60, $50 and $20. Bourcier said the top-priced tickets nearly all are sold and the advance sale represents $1,766,814. Requests for 4,500 more tickets have been received, he said. Sellout would represent $8.6 million.

Jerry Sachs, president of Capital Centre, said about 5,000 tickets have been sold for the closed-circuit telecast of the bout at the arena. There will be 19,000 seats available at the center.

Mike Malitz of Top Rank Inc. which is handling the closed-circuit telecast in the United States and Canada, said he had no overall figures available but reports of sales are "very, very good." There will be 310 sites with a combined capacity of 1,250,000 seats. Prices range from $15 to $30, he said.

Malitz said Madison Square Garden in New York City and its smaller arena, Felt Forum, have already sold out, a total of 24,000 seats. "All overall reports last week (from around the country) showed sales running ahead of every previous closed-circuit fight except the first Muhammad Ali-Joe Frazier bout in 1971," he said.

The Leonard-Duran bout will be shown on home television overseas. Malitz said South America and Europe will be blanketed with that telecast and it also will be seen in Japan, the Philippines, and Australia.

Sachs said Capital Centre will share with the Hyatt Corp., which operates arenas around the country, the rights to show the bout in Baltimore's Civic Center and other locations in the area, except Salisbury, Md.

Sachs said he has lined up other facilities in Washington and northern Virginia in case the demand justifies using them.

"But that is looking somewhat unlikely at this point," Sachs said. "We have a very large sale for Capital Centre this far in advance, but no sellout is assured; we have a lot of tickets to sell, about 14,000. We are ahead of what we drew for the third Ali-Frazier fight, 16,000, our largest closed-circuit telecast crowd."

Capital Centre tickets bought in advance will cost $25, but will be $30 the day of the bout.

Tickets may be purchased at the usual Capital Centre outlets -- at all Hecht's stores in Balitmore and Washington, at the Pentagon ticket office, and at 18th and K streets NW.