Leon Spinks said yesterday in Detroit that he will make the first defense of his title against Muhammad Ali.

Earlier, Top Rank, Inc., said in New York that it had reached a tentative agreement with Southern Sun Hotels Corp. to promote Spinks' first bout in Africa, most likely the new nation of Bophuthatswana.

There was an announcement by Southern Sun that No. 1 contender Ken Norton might fight in a preliminary bout to a $14-million rematch between Ali and Spinks and Bob Biron, manager of Norton, threatened to sue if his boxer does not get the first shot at Spinks.

He is ready to seek an injunction to prevent Spinks from fighting anyone else in the United States and to stop telecasts to this country if Spinks fights some other fighter abroad.

Biron said he has a binding agreement with Bob Arum, president of Top Rank, guaranteeing Norton the first challenge to Spinks. Norton has agreed to fight Spinks for a $200.000 purse.

"They have continued to perpetrate this fraud as anticipated," Biron said of Top Rank. "As far as we're concerned there is no card without Spinks honoring his commitment to meet Norton first.

"We have never been offered a fight on any alleged show, nor will we accept one if we are, other than with Spinks.

"We have a firm, binding, legal agreement with Arum, Top Rank and Spinks. We will exhaust our resources to see that the agreement is enforced. We intend to employ all legal remedies connected with this blatant breach of contract."

Spinks said at a news conference in Detroit, "It definitely will be Ali if I defend my title against anybody. Ali is the first."

Spinks announced at the news conference that he was breaking with attorney Milton Chwasky of New York and engaging Edward Bell, former Wayne County (Mich.) judge, who represents other athletes: Lem Barney and James Hunter of the Detroit Lions and Dave Bing of the Boston Celtics.

"All things being equal, it would ap- pear Ali should get the first shot," Bell said. "Ali was gracious enough to give Leon a shot."

Jose Sulaiman, president of the World Boxing Council, said in Mexico City the WBC is strongly considering stripping Spinks of his title on March 17 for backing out of an agreement to make his first title defense in May, against Norton.

In Panama City, the Work World Boxing Association approved yesterday the proposed Ali-Spinks rematch.

Dr. A. H. Rudnick of Las Vegas, where Spinks decisioned Ali, said he is convinced that Spinks' recently disclosed rib cartilage injury is legitimate. He said he told Spinks and Top Rank the day after the bout that the new champion should rest for two to three months.

Butch Lewis, vice president of Top Rank, said Spinks would hold a news conference later this week in New York City to clear the air.

Lewis said a few days ago he was told by Spinks to go ahead with plans for a fight with Norton. Asked about Norton yesterday, Spinks said, "I haven't decided anything yet. I'll take care of that later. I've got plenty of time for that."

WBC president Sulaiman said in Mexico that he is appointing a doctor to medically check Spinks to certify his injury and, if any, the time required for recovery.