An aide to Mayor Marion Barry said yesterday that ticket sales for Friday's light heavyweight title fight at the D.C. Armory between Michael Spinks and challenger Eddie Mustafa Muhammad are lagging, but a spokesman for the promoter said he's hoping that last-minute sales will bring the crowd close to the capacity of 10,000.

"Ticket sales are fair, not great," said Booker Griffin, an aide to promoter Butch Lewis, "but we're projecting that D.C. is a big walkup town. We're hoping to come close to 10,000."

Griffin said he did not have a figure on the number of tickets--priced at $100 for ringside seats, $50 and $25--sold as of yesterday.

But the mayor's aide, who declined to be identified, said city officials fear the live gate will not be enough to make up for concessions offered Lewis in an effort to bring Washington its first title fight since 1959.

The city council passed legislation last month reducing the D.C. Boxing and Wrestling Commission's 5-percent cut of the live gate to 2 percent after the first $100,000. Additionally, the D.C. Armory Board agreed to reduce Lewis' cost for use of the Armory from more than $25,000 to $12,000.

Barry, who lobbied aggressively to bring the fight to Washington, has been urging the city's businesses to buy blocks of tickets to support the fight and promote Washington's image nationally as a major sports town.

"I would be awfully embarrassed if we had a live championship fight and had the place empty," the mayor told a breakfast meeting of business leaders last week. "It will be an embarrassment if the TV cameras pan around the place and those seats are empty."