Sugar Ray Leonard, fulfilling his promise to fight his first title defense as world champion in his home town, will meet England's David Green tonight in Capital Centre for the World Boxing Council welterweight crown. t

The sturdy, aggressive Green enters the 15-round fight, which starts at approximately 10 p.m. as part of a four-hour ABC television (WJLA-TV-7) boxing extravaganza, with a 33-2 record, 26 knockouts and a ranking as the WBC's No. 10 contender.

Prior to the Leonard fight, ABC will show John Tate against Mike Weaver from Knoxville, Tenn., for the WBA heavyweight crown. Heavyweights Larry Holmes and Leroy Jones fight at approximately 11 from Las Vegas for the WBC title. ABC begins it boxing program at 8.

Green, the British champion at 147 pounds, has never before fought outside England and his list of victories is littered with the names of such fighters as Barton McAllister and Angus McMillan, who might seem more at home as butlers in a Dorothy Sayers mystery.

"A lot of people are asking, 'What's a Dave Boy Green?'" Leonard has said, grinning. "I guess I'm one of them."

Actually, Green fought for the WBC crown once before, in 1977, and acquitted himself well, battling Carlos Palomino into the 11th round before being knocked out.

"I've seen films of the fight," said Leonard's corner man, Angelo Dundee.

"Green was ahead on points until he walked into a hook."

Walking into hooks is an ancient British tradition. Green's trainer, Andy Smith, also handled heavyweight Joe Bugner. Bugner was even better at it, establishing himself as the prototypical horizontal British heavyweight.

Leonard, 26-0 as a pro, has called Green "a face fighter." This is open to two interpretations.Some think Leonard has implied that Green leads with his face.

"What Ray really means is that Dave Boy is always in your face, putting on pressure, because he's so aggressive," Dundee said.

Whichever is the case, if Green wins everybody in Leonard's camp should be strung up by their thumbs.

This match, for which Leonard expects to clear $1.4 million, is what the WBC calls an "optional defense." That means the champ can fight anybody in the world who suits his fancy -- and his wallet.

A new titlist is allowed one optional defense before his first "mandatory defense," which must be against the No. 1 contender. In other words, you get one free payday as champ, then you have to fight the meanest guy on the block.

Since the top contender is Roberto Duran, and since a dream fight between Leonard and "Stonehands" Duran probably would bring Leonard $5 million, it safely may be assumed that Green has been chosen for tonight's honor with enormous care.

The expectation is that Green will be a gutty foil for Leonard, offering a game fight, but that at some point in the proceedings he will walk into something he didn't see. Then, Green, who has never gone past 11 rounds, can return quietly to Chatteris.

Green, of course, knows this scenario and isn't fond of it. He's one knockout punch away from Leonard's crown and a great deal of rematch money. "Leonard's people made a bad mistake if they think I'm going to be easy," said the 26-year-old.

"I'm a great fighter . . . three-quarters of my wins have been knockouts . . . all it's going to take is one punch and it'll be over for Leonard," said Green, trying to fill those 19,743 Capital Centre seats scaled from $100 to $10.

In fact, Green has avoided Leonard while both have been training at the Sheraton Lanham. "He says he doesn't want to get to like me too much," Leonard said with a smile. "Guess he's a friendly bloke."

"Green's got a good right hand to the body and he doubles up on the hook," Dunee said. "He looks like an American fighter -- crawls all over you. He's got real long arms and impressive upper-body strength. Looks like a body builder. But he's only got a fairish jab."

In short, the 5-foot-8 Green may be a better version of all those sawed-off tanks that the 5 5-foot-8 Green may be a better version of all those sawed-off tanks that the 5-10 Leonard fought in his early professional days. Only Green doesn't figure to play trurtle and cover up.

The Leonard-Green bout will head a card that includes brother Roger Leonard, a rising junior middleweight, against distinguished local veteran Johnny Gant, who may now be playing the role of trial horse. In another 10-rounder, junior featherweight Derrick Holmes of Washington, who almost made the 1976 Olympic team with Leonard, meets Isaac Vega. Preliminaries start at 7 p.m.

More important to a national television audience, the Leonard fight will be part of a championship triple-header. The welterweight battle will be sandwiched between two versions of the heavyweight title.

The two heavyweight fights will be shown at the Centre on TelScreen.

Leonard, who claims to be in perfect shape, is looking forward to a crowd-pleasing fight after his rugged, close-to-the-vest war for the title with Wilfredo Benitez in November.

Green's trainer calls his man "a British version of Roberto Duran." This should be appreciated by those with a sense of irony. At this juncture, a Duran-the-man-slaughterer type is not what Leonard wants to have on his hands. The real article will come in due time.

On Saturday, Jose Sulaiman, president of the WBC, said he was giving the managements of Leonard and Duran until May 2 to negotiate a title fight. If they haven't come to terms -- and they've been stalemated for three months -- Sulaiman says a "mandatory defense" will be held under the WBC's system of "purse offerings."

The backroom battling between Leonard's attorney, Mike Trainer, and Duran's designated promoter, Don King, may be bloodier and harder-hitting than the Leonard-Green fight.

Leonard, as long as he remains unbeaten, has the leverage in these title bout wrestlings. He could have a fight with WBA champ Pepino Cuevas for that half of the world title, even if the WBC wouldn't sanction it. Then, he might have a rematch with Benitez, whose 39-1-1 record still has glitter.

Meanwhile, Duran would get a year older, as well as risking a defeat in the interim. Age is on Leonard's side.

"King may have to learn that a little bit of something is better than a whole lot of nothing," Trainer said.

King says Leonard's camp wants everything its own way, that it wants to call all the shots and fight opponents in exactly the progression that is most likely to bring victories and cash to Leonard.

For a few rounds tonight, David Green, a little British welter with a big heart and a strong punch, can make these multimillion-dollar wheeler-dealers hold their breath. He could throw a huge wrench into a very expensive machine.

Chances are he will not. Chances are he gamely will walk into a hook he never saw and join a noble tradition of horizontal Englishmen.