Larry Holmes, the World Boxing Council heaveyweight champion, sat in an easy chair this morning in his suite on the 69th floor of the Plaza Hotel. The flat Canadian plains stretched away across the Detroit River until they disappeared in mist.

"I want one more," said the man who the night before had successfully defended his title for the 10th time in three years, knocking out Leon Spinks with a third-round barrage of right-hand shots.

"Cooney," Holmes said, wistfully. "Cooney. Cooney. Cooney. Cooney."

Holmes is generally an easy-going guy outside the ring. His dealings with Spinks this week have been positively benign.

But when Jerry Cooney, the tall, undefeated contender from Huntington, N.Y., turned up in Detroit Thursday, Holmes grew suddenly menacing.

"I'll retire Cooney," Holmes said today.

In the boxing game, you regard everything first as hype. But the bad blood between Holmes and Cooney is too consistent to discount. Friday night, television commentator Howard Cosell wound up with a split lip when he got between the pair.

Cooney, who leaped to prominence with his thunderous 54-second knock-out of Ken Norton, says publicly that Holmes isn't very bright. He says the champion is promoter Don King 's pawn.

Homes resents Cooney's sudden rise. The champion is proud of the 27 fights it took him to earn his title shot, and his 38-0 record overall.

"Let Cooney fight the guys I fought on the way up," Holmes said this morning . "Let him fight some contenders. Let him fight a (Michael) Dokes, a (Greg) Page. Let's see if he really is a contender."

The pity is that the attractive Cooney-Holmes fight, a guaranteed smash gate attraction, is unlikely to happen anytime soon. Cooney is booked to fight WBA champion Mike Weaver in October and won't entertain any other offers until he's done with that.

Both fighters' camps contend the other is afraid of its man. King claims he's offered Cooney $5 million to fight Holmes after the Weaver bout; Cooney's manager, Ennis Rapaport, said today that Tiffany Productions is tendering a $5 1/2 million offer to Homes to fight Cooney.

"It's not that I won't fight him," Holmes said today. "He won't fight me. I signed the contract long ago to fight Weaver, (Quick) Tillis, Norton, Cooney -- any of those as they became available.

"I hate to hear him (Cooney) say, 'You need me.' I'm a rich man. I don't have to lace another pair of gloves on in my life. And he tells me I need him.

"He's never going to whip me. I can stay in this game another four years as a champ if I want to, because nobody's going to whip me."

Indeed, Holmes looked at his personal peak Friday night as he dispatched Spinks, the former gold medalist in the 1976 Olympics who was heavyweight champion for seven months in 1978.

Homes said he changed tactics in each of the three rounds against Spinks. "I like to demonstrate all of my talents because I knew the fight wouldn't last too long. I knew that from the start. I'm too big and too fast and I'm stronger than Leon Spinks."

Holmes said he got made in the second round when the bell mistakenly was rung 25 seconds before the round was over.

"He kept hitting me. I said, 'The bell rang.' So when it rang again, I hit him."

In the third round, Holmes staggered Spinks with a left hook, then followed him to his corner, decked the challenger with a right hand, and then measured and pummeled Spinks with a series of rights when the groggy challenger got back up after a ninecount.

This devastating display of power induced Spinks' cornermen to throw in the towel. The dispirited challenger disappeared after the right, bypassing a press conference and never appearing at his hotel.

"Leon," said his sparring partner, Vonzell Johnson, "went home. You know, home, home." Spinks lives in Detroit.

But the withering barrage didn't impress Cooney. "I thought Holmes looked good," the Long Islander said. "He hurt Leon twice, but I think when they stopped the fight he was regaining consciousness. They shouldn't have stopped it."

Holmes, his wife, Diane, and their 1 1/2-year-old daughter, Kandy, flew home to Easton, Pa., this morning. The champion has no fights scheduled and will be out of training for the first time since last March, when he began working out for an April 11 title defense against Trevor Berbick.

It will give him time to relax in the small-town surroundings he treasures.

He was asked if the victory over Spinks on national television would finally solidify his public recognition.

"If I was worried about that I'd stand out in the rain with just a tee-shirt on," he said. "I'd hang out on 42nd Street with the pimps.

"When I go out to dinner with my wife and nobody knows me, I love it. They'll recognize me in the record books. Thirty-eight and 0. I can't miss."