Boxing promoter Butch Lewis said yesterday he is "leaning very heavily" toward staging a light heavyweight title fight between champion Michael Spinks and the No. 1 contender, Eddie Mustafa Muhammad, at the D.C. Armory July 15.

Lewis said yesterday he will hold a press conference in Washington June 20 to make the formal announcement, but "as of right now, Washington is our choice. We have started negotiations with the (RFK) stadium people, and we think it's time for a title fight in the Nation's Capital."

The fight would be the first championship bout in the District of Columbia since Joe Louis beat Buddy Baer at old Griffith Stadium on May 23, 1941. Muhammad Ali fought two heavyweight title fights at Capital Centre, against Jimmy Young in 1976 and against Alfredo Evangelista in 1977.

"Why Washington?" Lewis asked. "Because Mayor (Marion) Barry has been chasing me around for more than a year to put a title fight there in D.C. I believe a title fight will do well there. We'll have a 2 1/2-hour show, we're getting an air-conditioning company to cool off the place, and I'm going to try to make it an event, a real show. We're hoping to get 15,000 in the place."

Spinks, 23-0 with 16 knockouts, won the WBA title by taking a unanimous decision from Muhammad in 1981. He has since unified the title by beating Dwight Braxton for the WBC championship March 18 in a fight Lewis promoted in Atlantic City. Muhammad is 43-6-1, with 35 knockouts, and has won his last four fights since losing to Spinks.